75000 - Document - Document and Entity Information link:presentationLink link:calculationLink link:definitionLink 75010 - Statement - Consolidated Statements of Comprehensive Income link:presentationLink link:calculationLink link:definitionLink 75020 - Statement - Consolidated Statements of Comprehensive Income 2 link:presentationLink link:calculationLink link:definitionLink 75030 - Statement - Consolidated Balance Sheets link:presentationLink link:calculationLink link:definitionLink 75040 - Statement - Consolidated Balance Sheets (Parenthetical) link:presentationLink link:calculationLink link:definitionLink 75050 - Statement - Consolidated Statements of Cash Flows link:presentationLink link:calculationLink link:definitionLink 75060 - Statement - Consolidated Statements of Changes in Equity link:presentationLink link:calculationLink link:definitionLink 75070 - Statement - Consolidated Statements of Changes in Equity (Parenthetical) link:presentationLink link:calculationLink link:definitionLink 995457 - Disclosure - Cybersecurity Risk Management, Strategy, and Governance link:presentationLink link:calculationLink link:definitionLink 995467 - Disclosure - Nature of Operations link:presentationLink link:calculationLink link:definitionLink 995477 - Disclosure - Basis of Presentation, Significant Accounting Policies and Recent Accounting Pronouncements link:presentationLink link:calculationLink link:definitionLink 995487 - Disclosure - Acquisitions and Divestitures link:presentationLink link:calculationLink link:definitionLink 995497 - Disclosure - Revenue link:presentationLink link:calculationLink link:definitionLink 995507 - Disclosure - Segment Information link:presentationLink link:calculationLink link:definitionLink 995517 - Disclosure - Restructuring Costs link:presentationLink link:calculationLink link:definitionLink 995527 - Disclosure - Income Taxes link:presentationLink link:calculationLink link:definitionLink 995537 - Disclosure - Fixed Assets link:presentationLink link:calculationLink link:definitionLink 995547 - Disclosure - Goodwill and Other Intangible Assets link:presentationLink link:calculationLink link:definitionLink 995557 - Disclosure - Derivative Financial Instruments link:presentationLink link:calculationLink link:definitionLink 995567 - Disclosure - Debt link:presentationLink link:calculationLink link:definitionLink 995577 - Disclosure - Fair Value Measurements link:presentationLink link:calculationLink link:definitionLink 995587 - Disclosure - Retirement Benefits link:presentationLink link:calculationLink link:definitionLink 995597 - Disclosure - Leases link:presentationLink link:calculationLink link:definitionLink 995607 - Disclosure - Commitments and Contingencies link:presentationLink link:calculationLink link:definitionLink 995617 - Disclosure - Supplementary Information for Certain Balance Sheet Accounts link:presentationLink link:calculationLink link:definitionLink 995627 - Disclosure - Other (Loss)/Income, Net link:presentationLink link:calculationLink link:definitionLink 995637 - Disclosure - Accumulated Other Comprehensive Loss link:presentationLink link:calculationLink link:definitionLink 995647 - Disclosure - Share-based Compensation link:presentationLink link:calculationLink link:definitionLink 995657 - Disclosure - Earnings Per Share link:presentationLink link:calculationLink link:definitionLink 995667 - Disclosure - Supplemental Disclosures of Cash Flow Information link:presentationLink link:calculationLink link:definitionLink 995677 - Disclosure - Subsequent Events link:presentationLink link:calculationLink link:definitionLink 995687 - Disclosure - Quarterly Financial Data (Unaudited) link:presentationLink link:calculationLink link:definitionLink 995697 - Disclosure - Basis of Presentation, Significant Accounting Policies and Recent Accounting Pronouncements (Policies) link:presentationLink link:calculationLink link:definitionLink 995707 - Disclosure - Basis of Presentation, Significant Accounting Policies and Recent Accounting Pronouncements (Tables) link:presentationLink link:calculationLink link:definitionLink 995717 - Disclosure - Acquisitions and Divestitures (Tables) link:presentationLink link:calculationLink link:definitionLink 995727 - Disclosure - Revenue (Tables) link:presentationLink link:calculationLink link:definitionLink 995737 - Disclosure - Segment Information (Tables) link:presentationLink link:calculationLink link:definitionLink 995747 - Disclosure - Income Taxes (Tables) link:presentationLink link:calculationLink link:definitionLink 995757 - Disclosure - Fixed Assets (Tables) link:presentationLink link:calculationLink link:definitionLink 995767 - Disclosure - Restructuring Costs (Tables) link:presentationLink link:calculationLink link:definitionLink 995777 - Disclosure - Goodwill and Other Intangible Assets (Tables) link:presentationLink link:calculationLink link:definitionLink 995787 - Disclosure - Derivative Financial Instruments (Tables) link:presentationLink link:calculationLink link:definitionLink 995797 - Disclosure - Debt (Tables) link:presentationLink link:calculationLink link:definitionLink 995807 - Disclosure - Fair Value Measurements (Tables) link:presentationLink link:calculationLink link:definitionLink 995817 - Disclosure - Retirement Benefits (Tables) link:presentationLink link:calculationLink link:definitionLink 995827 - Disclosure - Leases (Tables) link:presentationLink link:calculationLink link:definitionLink 995837 - Disclosure - Supplementary Information for Certain Balance Sheet Accounts (Tables) link:presentationLink link:calculationLink link:definitionLink 995847 - Disclosure - Other (Loss)/Income, Net (Tables) link:presentationLink link:calculationLink link:definitionLink 995857 - Disclosure - Accumulated Other Comprehensive Loss (Tables) link:presentationLink link:calculationLink link:definitionLink 995867 - Disclosure - Share-based Compensation (Tables) link:presentationLink link:calculationLink link:definitionLink 995877 - Disclosure - Earnings Per Share (Tables) link:presentationLink link:calculationLink link:definitionLink 995887 - Disclosure - Supplemental Disclosures of Cash Flow Information (Tables) link:presentationLink link:calculationLink link:definitionLink 995897 - Disclosure - Quarterly Financial Data (Unaudited) (Tables) link:presentationLink link:calculationLink link:definitionLink 995907 - Disclosure - Nature of Operations (Details) link:presentationLink link:calculationLink link:definitionLink 995917 - Disclosure - Basis of Presentation, Significant Accounting Policies and Recent Accounting Pronouncements - Narrative (Details) link:presentationLink link:calculationLink link:definitionLink 995927 - Disclosure - Basis of Presentation, Significant Accounting Policies and Recent Accounting Pronouncements - Schedule of Acquired Intangible Assets Amortized (Details) link:presentationLink link:calculationLink link:definitionLink 995937 - Disclosure - Acquisitions and Divestitures - (Additional Information) (Details) link:presentationLink link:calculationLink link:definitionLink 995947 - Disclosure - Acquisitions and Divestitures - TRANZACT Divestiture (Details) link:presentationLink link:calculationLink link:definitionLink 995957 - Disclosure - Acquisitions and Divestitures - Financial Information Related to Operation of TRANZACT (Details) link:presentationLink link:calculationLink link:definitionLink 995967 - Disclosure - Acquisitions and Divestitures - Willis Re Divestiture (Details) link:presentationLink link:calculationLink link:definitionLink 995977 - Disclosure - Acquisitions and Divestitures - Other Disposals (Details) link:presentationLink link:calculationLink link:definitionLink 995987 - Disclosure - Revenue - Schedule of Disaggregation of Revenue (Details) link:presentationLink link:calculationLink link:definitionLink 995997 - Disclosure - Revenue - Schedule of Components of Interest and Other Income (Details) link:presentationLink link:calculationLink link:definitionLink 996007 - Disclosure - Revenue - Schedule of Revenue by Geography (Detail) link:presentationLink link:calculationLink link:definitionLink 996017 - Disclosure - Revenue - Schedule of Contract Balances (Details) link:presentationLink link:calculationLink link:definitionLink 996027 - Disclosure - Revenue - Schedule of Contract Balances (Parenthetical) (Details) link:presentationLink link:calculationLink link:definitionLink 996037 - Disclosure - Revenue - Narrative (Details) link:presentationLink link:calculationLink link:definitionLink 996047 - Disclosure - Revenue - Schedule of Changes in Allowance for Doubtful Accounts (Details) link:presentationLink link:calculationLink link:definitionLink 996057 - Disclosure - Revenue - Schedule of Remaining Performance Obligations (Details) link:presentationLink link:calculationLink link:definitionLink 996067 - Disclosure - Revenue - Schedule of Remaining Performance Obligations (Details) 1 link:presentationLink link:calculationLink link:definitionLink 996077 - Disclosure - Revenue - Schedule of Capitalized and Deferred Costs (Details) link:presentationLink link:calculationLink link:definitionLink 996087 - Disclosure - Segment Information - Narrative (Details) link:presentationLink link:calculationLink link:definitionLink 996097 - Disclosure - Segment Information - Revenue (Net of Reimbursable Expenses) of the Reported Segments (Details) link:presentationLink link:calculationLink link:definitionLink 996107 - Disclosure - Segment Information - Reconciliation of Information Reported by Segment to Consolidated Amounts (Details) link:presentationLink link:calculationLink link:definitionLink 996117 - Disclosure - Segment Information - Reconciliation of Information Reported by Segment to Consolidated Amounts (Parenthetical) (Details) link:presentationLink link:calculationLink link:definitionLink 996127 - Disclosure - Segment Information - Revenue and Tangible Long-lived Assets by Geographical Areas (Details) link:presentationLink link:calculationLink link:definitionLink 996137 - Disclosure - Restructuring Costs - Narrative (Details) link:presentationLink link:calculationLink link:definitionLink 996147 - Disclosure - Restructuring Costs - Summary of Total Restructuring Costs (Details) link:presentationLink link:calculationLink link:definitionLink 996157 - Disclosure - Restructuring Costs - Rollforward of Liability Associated with Cash-based Charges (Details) link:presentationLink link:calculationLink link:definitionLink 996167 - Disclosure - Income Taxes - Income (Loss) from Operations Before Income Taxes (Details) link:presentationLink link:calculationLink link:definitionLink 996177 - Disclosure - Income Taxes - Provision for Benefit from Income Taxes (Details) link:presentationLink link:calculationLink link:definitionLink 996187 - Disclosure - Income Taxes - Effective Tax Rate Reconciliation (Details) link:presentationLink link:calculationLink link:definitionLink 996197 - Disclosure - Income Taxes - Narrative (Details) link:presentationLink link:calculationLink link:definitionLink 996207 - Disclosure - Income Taxes - Deferred Tax Assets (Liabilities) (Details) link:presentationLink link:calculationLink link:definitionLink 996217 - Disclosure - Income Taxes - Deferred Tax Liabilities, Balance Sheet Classification (Details) link:presentationLink link:calculationLink link:definitionLink 996227 - Disclosure - Income Taxes - Valuation Allowance (Details) link:presentationLink link:calculationLink link:definitionLink 996237 - Disclosure - Income Taxes - Unrecognized Tax Benefits (Details) link:presentationLink link:calculationLink link:definitionLink 996247 - Disclosure - Income Taxes - Summary of Tax Years that Remain Open to Tax Examination in Major Tax Jurisdictions (Details) link:presentationLink link:calculationLink link:definitionLink 996257 - Disclosure - Income Taxes - Summary of Cash Paid for Income Taxes, Net of Refunds (Details) link:presentationLink link:calculationLink link:definitionLink 996267 - Disclosure - Fixed Assets - Components of Fixed Assets (Details) link:presentationLink link:calculationLink link:definitionLink 996277 - Disclosure - Fixed Assets - Components of Fixed Assets (Parenthetical) (Details) link:presentationLink link:calculationLink link:definitionLink 996287 - Disclosure - Fixed Assets - Assets Held Under Finance Leases (Details) link:presentationLink link:calculationLink link:definitionLink 996297 - Disclosure - Goodwill and Other Intangible Assets - Components of Goodwill (Details) link:presentationLink link:calculationLink link:definitionLink 996307 - Disclosure - Goodwill and Other Intangible Assets - Components of Goodwill (Parenthetical) (Details) link:presentationLink link:calculationLink link:definitionLink 996317 - Disclosure - Goodwill and Other Intangible Assets - Changes in the Net Carrying Amount of the Components of Finite-Lived Intangible Assets (Details) link:presentationLink link:calculationLink link:definitionLink 996327 - Disclosure - Goodwill and Other Intangible Assets - Narrative (Details) link:presentationLink link:calculationLink link:definitionLink 996337 - Disclosure - Goodwill and Other Intangible Assets - Schedule of Future Estimated Amortization Expense for Amortizable Intangible Assets (Details) link:presentationLink link:calculationLink link:definitionLink 996347 - Disclosure - Derivative Financial Instruments - Narrative (Details) link:presentationLink link:calculationLink link:definitionLink 996357 - Disclosure - Derivative Financial Instruments - Schedule of Derivative Instruments Designated As Hedging Instrument Effect on Condensed Consolidated Statements of Comprehensive Income (Details) link:presentationLink link:calculationLink link:definitionLink 996367 - Disclosure - Derivative Financial Instruments - Schedule of Derivative Instruments, Effect on Condensed Consolidated Statements of Comprehensive Income (Details) link:presentationLink link:calculationLink link:definitionLink 996377 - Disclosure - Debt - Schedule of Current and Long-term Debt (Details) link:presentationLink link:calculationLink link:definitionLink 996387 - Disclosure - Debt - Narrative (Details) link:presentationLink link:calculationLink link:definitionLink 996397 - Disclosure - Debt - Maturities of Long Term Debt (Details) link:presentationLink link:calculationLink link:definitionLink 996407 - Disclosure - Debt - Interest Expense (Details) link:presentationLink link:calculationLink link:definitionLink 996417 - Disclosure - Fair Value Measurements - Schedule of Assets and Liabilities Measured at Fair Value on Recurring Basis (Details) link:presentationLink link:calculationLink link:definitionLink 996427 - Disclosure - Fair Value Measurements - Fair Value Liabilities Measured Using Significant Unobservable Inputs Level 3 (Details) link:presentationLink link:calculationLink link:definitionLink 996437 - Disclosure - Fair Value Measurements - Narrative (Details) link:presentationLink link:calculationLink link:definitionLink 996447 - Disclosure - Fair Value Measurements and Investments - Summarizes the Types of Holdings and Related Values (Details) link:presentationLink link:calculationLink link:definitionLink 996457 - Disclosure - Fair Value Measurements - Schedule of Assets and Liabilities Whose Carrying Values Differ From the Fair Value and are Not Measured on a Recurring Basis (Details) link:presentationLink link:calculationLink link:definitionLink 996467 - Disclosure - Retirement Benefits - Narrative (Details) link:presentationLink link:calculationLink link:definitionLink 996477 - Disclosure - Retirement Benefits - Change in Benefit Obligation and Plan Assets (Details) link:presentationLink link:calculationLink link:definitionLink 996487 - Disclosure - Retirement Benefits - Amounts Recognized in Other Comprehensive Income (Loss) (Details) link:presentationLink link:calculationLink link:definitionLink 996497 - Disclosure - Retirement Benefits - Benefit Obligation In Excess Of Plan Assets (Details) link:presentationLink link:calculationLink link:definitionLink 996507 - Disclosure - Retirement Benefits - Accumulated Benefit Obligation In Excess of Plan Assets (Details) link:presentationLink link:calculationLink link:definitionLink 996517 - Disclosure - Retirement Benefits - Net Periodic Benefit Cost (Details) link:presentationLink link:calculationLink link:definitionLink 996527 - Disclosure - Retirement Benefits - Assumptions Used (Details) link:presentationLink link:calculationLink link:definitionLink 996537 - Disclosure - Retirement Benefits - Allocation of Plan Assets (Details) link:presentationLink link:calculationLink link:definitionLink 996547 - Disclosure - Retirement Benefits - Fair Value (Details) link:presentationLink link:calculationLink link:definitionLink 996557 - Disclosure - Retirement Benefits - Fair Value Reconciliation (Details) link:presentationLink link:calculationLink link:definitionLink 996567 - Disclosure - Retirement Benefits - Significant Unobservable Input Reconciliation (Details) link:presentationLink link:calculationLink link:definitionLink 996577 - Disclosure - Retirement Benefits - Projected Benefit Obligation (Details) link:presentationLink link:calculationLink link:definitionLink 996587 - Disclosure - Retirement Benefits - Expected Benefit Payments (Details) link:presentationLink link:calculationLink link:definitionLink 996597 - Disclosure - Leases - Schedule of Lease (Details) link:presentationLink link:calculationLink link:definitionLink 996607 - Disclosure - Leases - Schedule of Amount Recorded in Consolidated Statements of Comprehensive Income (Details) link:presentationLink link:calculationLink link:definitionLink 996617 - Disclosure - Leases - Narrative (Details) link:presentationLink link:calculationLink link:definitionLink 996627 - Disclosure - Leases -Schedule of Cash Paid in the Measurement of Lease Liabilities (Details) link:presentationLink link:calculationLink link:definitionLink 996637 - Disclosure - Leases - Schedule of Weighted Average Term and Discount Rates (Details) link:presentationLink link:calculationLink link:definitionLink 996647 - Disclosure - Leases - Schedule of Maturity of Operating and Finance Leases Liabilities (Details) link:presentationLink link:calculationLink link:definitionLink 996657 - Disclosure - Leases - Schedule of Maturity of Operating and Finance Leases Liabilities (Details) 2 link:presentationLink link:calculationLink link:definitionLink 996667 - Disclosure - Commitments and Contingencies - Narrative (Details) link:presentationLink link:calculationLink link:definitionLink 996677 - Disclosure - Supplementary Information for Certain Balance Sheet Accounts - Prepaid and Other Current Assets (Details) link:presentationLink link:calculationLink link:definitionLink 996687 - Disclosure - Supplementary Information for Certain Balance Sheet Accounts - Other Non-current Assets (Details) link:presentationLink link:calculationLink link:definitionLink 996697 - Disclosure - Supplementary Information for Certain Balance Sheet Accounts - Deferred Revenue and Accrued Expenses (Details) link:presentationLink link:calculationLink link:definitionLink 996707 - Disclosure - Supplementary Information for Certain Balance Sheet Accounts - Other Current Liabilities (Details) link:presentationLink link:calculationLink link:definitionLink 996717 - Disclosure - Supplementary Information for Certain Balance Sheet Accounts - Provision For Liabilities (Details) link:presentationLink link:calculationLink link:definitionLink 996727 - Disclosure - Supplementary Information for Certain Balance Sheet Accounts - Other Non-current Liabilities (Details) link:presentationLink link:calculationLink link:definitionLink 996737 - Disclosure - Other (Loss)/Income, Net (Details) link:presentationLink link:calculationLink link:definitionLink 996747 - Disclosure - Other (Loss)/Income, Net (Parenthetical) (Details) link:presentationLink link:calculationLink link:definitionLink 996757 - Disclosure - Accumulated Other Comprehensive Loss - Components of Other Comprehensive (Loss) Income (Details) link:presentationLink link:calculationLink link:definitionLink 996767 - Disclosure - Accumulated Other Comprehensive Loss - Schedule of Accumulated Other Comprehensive Income (Loss) (Details) link:presentationLink link:calculationLink link:definitionLink 996777 - Disclosure - Accumulated Other Comprehensive Loss - Schedule of Accumulated Other Comprehensive Income (Loss) (Parenthetical) (Details) link:presentationLink link:calculationLink link:definitionLink 996787 - Disclosure - Share-based Compensation - Narrative (Details) link:presentationLink link:calculationLink link:definitionLink 996797 - Disclosure - Share-based Compensation - Assumptions (Details) link:presentationLink link:calculationLink link:definitionLink 996807 - Disclosure - Share-based Compensation - Nonvested Restricted Stock Units and Performance Based Stock Units Activity (Details) link:presentationLink link:calculationLink link:definitionLink 996817 - Disclosure - Earnings Per Share - Basic and Diluted Earnings Per Share (Details) link:presentationLink link:calculationLink link:definitionLink 996827 - Disclosure - Earnings Per Share - Narrative (Details) link:presentationLink link:calculationLink link:definitionLink 996837 - Disclosure - Supplemental Disclosures of Cash Flow Information (Details) link:presentationLink link:calculationLink link:definitionLink 996847 - Disclosure - Subsequent Events - Narrative (Details) link:presentationLink link:calculationLink link:definitionLink Accrued revenue not currently taxable Deferred Tax Liabilities, Tax Deferred Income Accrued revenue not currently taxable Capitalized Contract Cost Capitalized Contract Cost [Table Text Block] Vested, Weighted Average Grant Date Fair Value (in dollars per share) Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Vested in Period, Weighted Average Grant Date Fair Value Supplemental Disclosures Regarding Cash Flow Information and Non-cash Flow Investing and Financing Activities Schedule of Cash Flow, Supplemental Disclosures [Table Text Block] Total Lease, Interest Lease Liability Undiscounted Excess Amount Amount of lessee's undiscounted obligation for lease payments in excess of discounted obligation for lease payments for both operating lease and finance lease. Retirement Plan Type Retirement Plan Type [Axis] Segments Segments [Domain] Net Income (Loss), Including Portion Attributable to Nonredeemable Noncontrolling Interest, Total Net Income (Loss), Including Portion Attributable to Nonredeemable Noncontrolling Interest Net (loss)/income Internally developed software [Member] Software Development [Member] Projected benefit obligation at end of year Defined Benefit Plan, Pension Plan with Projected Benefit Obligation in Excess of Plan Assets, Projected Benefit Obligation Ending Balance Beginning Balance Restructuring Reserve Restructuring Reserve, Total Accrued retirement benefits Accrued Employee Benefits, Current Concentration Risk Type [Axis] Repurchase agreements [Member] Repurchase Agreements [Member] Schedule of Revenues from External Customers and Long-Lived Assets [Table] Finance Lease, Liability, Total Finance Lease, Total lease liabilities Finance Lease, Liability Process Optimization Member Process Optimization Member Process Optimization [Member] Entity Incorporation, State or Country Code Entity Incorporation, State or Country Code Finance Lease, Liability, to be Paid, Year Four Finance Lease, 2029 Preferred Stock, Shares Issued, Total Preference shares, shares issued Preferred Stock, Shares Issued Depreciation Depreciation Not Including Integration Component Depreciation, not including integration component. Balance Sheet Location Statement of Financial Position Location, Balance [Domain] Term for renewal commissions expected Term For Renewal Commissions Expected Term for renewal commissions expected. Employer contributions Defined Benefit Plan, Plan Assets, Contributions by Employer Balance as of beginning of period Balance as of end of period Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability Value Amount payable from option Amount Payable From Option Amount payable from option. Defined Contribution Plan Tranches Defined Contribution Plan Tranches [Domain] Defined contribution plan tranches. Restructuring, description Restructuring and Related Activities, Description Long-term Debt, Excluding Current Maturities, Total Long-term debt, excluding current maturities Long-term debt Long-Term Debt, Excluding Current Maturities Plan Name Plan Name [Axis] Equity [Abstract] Entity Current Reporting Status Entity Current Reporting Status Goodwill, gross, beginning balance Goodwill, gross, ending balance Goodwill, Gross Net assets held in investments Defined Benefit Plan Net Assets Held In Investments Defined benefit plan net assets held in investments. 3.500% senior notes due 2021 [Member] Senior Notes Due202103500 [Member] Senior notes due 2021, 03500. Level 2 [Member] Fair Value, Inputs, Level 2 [Member] Other non-current assets Net deferred tax assets Deferred Tax Assets, Net of Valuation Allowance Deferred Tax Assets, Net of Valuation Allowance Commitments and Contingencies Commitments and Contingencies Disclosure [Text Block] Pooled / commingled funds [Member] Commingled Funds [Member] Commingled funds. Cash Flow Hedging [Member] Cash Flow Hedging [Member] Ordinary shares, shares authorized Common Stock, Shares Authorized Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward] Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward] Finite-Lived Intangible Asset, Expected Amortization, Year Four 2029 Capital loss carryforwards Deferred Tax Assets, Capital Loss Carryforwards Product and Service Product and Service [Axis] Fair Value by Liability Class Fair Value by Liability Class [Domain] Document Fiscal Period Focus Document Fiscal Period Focus Capital lease obligations Finance Lease, Total future lease payments Finance Lease, Liability, to be Paid Defined Benefit Plan, Expected Future Benefit Payment, after Year Five for Next Five Years Years 2031 - 2035 Expected long-term rate of return on assets Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Expected Long-Term Rate of Return on Plan Assets Other Noncurrent Liabilities [Member] Other Non-current liabilities [Member] Current liability for pension benefits Liability, Defined Benefit Plan, Current Stated interest rate Debt Instrument, Interest Rate, Stated Percentage Revenue from Contract with Customer [Abstract] Entity Shell Company Entity Shell Company Rest of World [Member] Rest Of World [Member] Rest of world. Other Comprehensive (Income) Loss, Defined Benefit Plan, after Reclassification Adjustment, before Tax Total recognized in other comprehensive loss/(income) SEC Schedule, 12-09, Valuation Allowances and Reserves Type SEC Schedule, 12-09, Valuation Allowances and Reserves Type [Axis] Service [Member] Service [Member] Short-term securities [Member] Short-Term Investments [Member] Cash and Cash Equivalents, at Carrying Value, Ending Balance Cash and Cash Equivalents, at Carrying Value, Beginning Balance Cash and Cash Equivalents, at Carrying Value, Total Unencumbered and available funds required Cash and cash equivalents Cash and Cash Equivalent Discontinued Operations [Member] Discontinued Operations [Member] Net actuarial loss Defined Benefit Plan, Accumulated Other Comprehensive Income (Loss), Gain (Loss), before Tax Schedule of Maturities of Long-term Debt Schedule of Maturities of Long-Term Debt [Table Text Block] Dividends attributable to non-controlling interests Noncontrolling Interest, Decrease from Distributions to Noncontrolling Interest Holders Benefit obligation, beginning of year Benefit obligation, end of year Defined Benefit Plan, Benefit Obligation Number of reporting units Number of Reporting Units Debt instrument maturity year Debt Instrument Maturity Year Debt instrument maturity year. Cost Impaired Assets to be Disposed of by Method Other than Sale, Carrying Value of Asset Defined Benefit Plan, Expected Future Benefit Payment, Year Two 2027 Cybersecurity Risk Management, Strategy, and Governance [Abstract] Common Stock, Shares, Issued, Total Ordinary shares, shares issued Common Stock, Shares, Issued Cybersecurity Risk Management Positions or Committees Responsible Report to Board [Flag] Cybersecurity Risk Board of Directors Oversight [Text Block] UNITED KINGDOM [Member] Foreign Plan [Member] Asset Class [Domain] Statement [Table] Statement [Table] Nature of Uncertainty Nature of Uncertainty [Axis] Increases related to tax positions in current year Increases related to current year tax positions Unrecognized Tax Benefits, Increase Resulting from Current Period Tax Positions Non-cash additions to operating lease ROU assets Right-of-Use Asset Obtained in Exchange for Operating Lease Liability Internal Revenue Service (IRS) [Member] Internal Revenue Service (IRS) [Member] Finance Leases Schedule Of Finance Leased Assets Table [Text Block] Schedule of finance leased assets. AOCL [Member] AOCI Including Portion Attributable to Noncontrolling Interest [Member] Minority Interest [Table] Noncontrolling Interest [Table] Other provisions Other Accrued Liabilities, Noncurrent Senior Notes Due 203104550 [Member] Senior notes due 2031, 04550. 4.550% senior notes due 2031 [Member] Acquisitions, cash payment Payments to Acquire Businesses, Gross cash payments totaling Proceeds from debt, net of issuance costs Proceeds from Debt, Net of Issuance Costs Restructuring, Expected future effects Restructuring, Expected future effects Debt Securities, Held-to-Maturity, Amortized Cost, after Allowance for Credit Loss, Maturity, Allocated and Single Maturity Date, after Year One through Five Due in one year through five years carrying value Capitalized Contract Cost, Net, Total Capitalized Contract Cost, Net Capitalized Contract Cost, Net Capitalized Contract Cost, Net Statement [Line Items] Statement [Line Items] Business Acquisition, Acquiree Business Combination [Domain] Revenue Recognition Revenue from Contract with Customer [Policy Text Block] Alexis Faber [Member] Alexis Faber Alexis Faber Remeasurement of Deferred Tax Assets and Liabilities [Member] Remeasurement of Deferred Tax Assets and Liabilities. Foreign exchange Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Gain (Loss) Included in Other Comprehensive Income (Loss) Other income, net [Member] Other Expense [Member] Entity Filer Category Entity Filer Category Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward] Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward] Settlement Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Gain (Loss) Due to Settlement Reclassification from AOCI, Current Period, Net of Tax, Attributable to Parent (Gain)/loss reclassified from accumulated other comprehensive loss (net of income tax) TOTAL LIABILITIES AND EQUITY Liabilities and Equity Debt Instrument [Line Items] Debt Instrument [Line Items] Long-term Debt, Current Maturities, Total Current debt Long-Term Debt, Current Maturities Effective Income Tax Rate Reconciliation, Tax Contingency, Percent Effective Income Tax Rate Reconciliation, Tax Contingency, Percent, Total Changes in unrecognized tax benefits, Percentage Changes in unrecognized tax benefits, Percentage Long-Term Debt, Maturity, Year Three 2028 5.750% senior notes due 2021 [Member] Senior Notes Due202105750 [Member] Senior notes due 2021, 05750. Restructuring Type Restructuring Type [Axis] Long-Lived Tangible Asset Long-Lived Tangible Asset [Axis] Finance Lease, Liability, to be Paid, Year Three Finance Lease, 2028 Increase (decrease) in valuation allowance Valuation Allowance, Deferred Tax Asset, Increase (Decrease), Amount Operating Loss Carryforwards [Table] Operating Loss Carryforwards [Table] Hedging Relationship Hedging Relationship [Axis] One Year Term Loan [Member] One Year Term Loan [Member] One-year term loan. Prepaid Expenses and Other Current Assets [Member] Prepaid Expenses and Other Current Assets [Member] Cybersecurity Risk Third Party Oversight and Identification Processes [Flag] Quarterly Financial Information Disclosure [Abstract] Summary of Total Restructuring Costs Restructuring and Related Costs [Table Text Block] Deferred Revenue [Domain] Revenues, Excluding Interest and Dividends Revenues, Excluding Interest and Dividends, Total Segment revenue excluding interest income Derivative [Line Items] Derivative [Line Items] BDA [Member] Benefits Delivery And Administration [Member] Benefits delivery and administration. Deferred Tax Assets, Valuation Allowance, Total Less: valuation allowance Valuation allowance Deferred Tax Assets, Valuation Allowance Defined Benefit Plan, Net Periodic Benefit Cost (Credit) Excluding Service Cost, Statement of Income or Comprehensive Income [Extensible Enumeration] Prepayment of outstanding debt Extinguishment of Debt, Amount U.S. federal statutory income tax rate U.S. statutory tax rate Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent Foreign statutory income tax rate, Percentage Subsequent Event [Line Items] Effective Income Tax Rate Reconciliation, Nondeductible Expense, Amount, Total Non-deductible expenses and dividends Effective Income Tax Rate Reconciliation, Nondeductible Expense, Amount Cybersecurity Risk Management Third Party Engaged [Flag] Documents Incorporated by Reference [Text Block] Documents Incorporated by Reference Goodwill Goodwill, net, beginning balance Goodwill, Total Goodwill, net, ending balance Goodwill Goodwill after impairment Other Noncash Income (Expense), Total Other, net Other Noncash Income (Expense) Effective Income Tax Rate Reconciliation, Percent Total provision for income taxes, Percentage Total provision for income taxes, Percentage Total Lease, Total future lease payments Lease Liability Payments Due Amount of lessee's undiscounted obligation for lease payments for both operating lease and finance lease. Finance Lease, Liability, Current, Statement of Financial Position [Extensible Enumeration] Subpart F Income Subpart F Amount Effective Income Tax Rate Reconciliation on Subpart F Amount Effective Income Tax Rate Reconciliation on Subpart F Amount Income Tax Authority Income Tax Jurisdiction [Axis] 1-year Term Loan Facility Matures 2016, Tranche two [Member] One Year Term Loan Facility Due2016 Tranche Two [Member] One Year Term Loan Facility Due 2016, Tranche Two [Member] Senior Notes Due202804500 [Member] Senior notes due 2028, 04500. 4.500% senior notes due 2028 [Member] Operating loss carryforwards, not subject to expiration Deferred Tax Assets, Operating Loss Carryforwards, Not Subject to Expiration Geographical Geographical [Domain] Debt Instrument Additional Basis Spread On Variable Rate1 Debt Instrument Additional Basis Spread On Variable Rate1 Debt instrument additional basis spread on variable rate1. Retirement Plan Tax Status Retirement Plan Tax Status [Domain] Net Operating Income of the Reported Segments Reconciliation of Operating Profit (Loss) from Segments to Consolidated [Table Text Block] Other Comprehensive Income (Loss), before Tax, Total Other Comprehensive Income (Loss), before Tax Other comprehensive income/(loss) before tax Other Pension Plan [Member] Pension Plan [Member] Business Combination, Achieved in Stages, Preacquisition Equity Interest in Acquiree, Percentage Reamining controlling interest Defined Benefit Plan Assumptions Used Calculating Net Periodic Benefit Cost Discount Rate Interest Cost On Projected Benefit Obligation Discount rate - interest cost on PBO Defined benefit plan, assumptions used calculating net periodic benefit cost, discount rate, interest cost on projected benefit obligation. Accounts Receivable, Allowance for Credit Loss, Ending Balance Accounts Receivable, Allowance for Credit Loss, Beginning Balance Allowance for doubtful debts Accounts Receivable, Allowance for Credit Loss Time-based Stock Options [Member] Time Based Stock Options [Member] Time based stock options. Additional Paid in Capital, Common Stock, Ending Balance Additional Paid in Capital, Common Stock, Beginning Balance Additional paid-in capital Additional Paid in Capital, Common Stock Deferred contract costs Capitalized Contract Cost, Net, Noncurrent Merger-Related Securities Litigation [Member] Willis Towers Watson Merger Related Securities Litigation [Member] Willis Towers Watson merger-related securities litigation. Benefits paid Defined Benefit Plan, Plan Assets, Benefits Paid Transaction and Transformation [Member] Transaction and Transformation. Property,Plant and Equipment [LineItems] Property, Plant and Equipment [Line Items] Continuing operation. Continuing Operation [Member] Continuing Operation [Member] Weighted average remaining life of amortizable intangible assets and liabilities Finite-Lived Intangible Asset, Useful Life Stock options granted Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Grants in Period, Gross Disaggregation Of Revenue [Table] Disaggregation of Revenue [Table] Newly-eligible employees [Member] Newly Eligible Employees [Member] Newly-eligible employees. Cybersecurity Risk Management, Strategy, and Governance [Table] Schedule of Basic and Diluted Earnings Per Share Schedule of Earnings Per Share, Basic and Diluted [Table Text Block] Additions charged to costs and expenses SEC Schedule, 12-09, Valuation Allowances and Reserves, Additions, Charge to Cost and Expense Equity securities [Member] Equity Securities [Member] AOCI Attributable to Parent, Net of Tax [Roll Forward] AOCI Attributable to Parent, Net of Tax [Roll Forward] Trademark and trade name [Member] Trademarks and Trade Names [Member] Summary of Entities Summary of Entities [Table Text Block] Summary of entities. Prior service cost Other Comprehensive (Income) Loss, Defined Benefit Plan, Prior Service Cost (Credit), before Tax 5.350% senior notes due 2033 [Member] Senior Notes Due 203305350[Member] Senior notes due 2033, 05350. — Basic: income from continuing operations Earnings Per Share, Basic Basic earnings/(loss) per share Disaggregation of Revenue Disaggregation of Revenue [Table Text Block] Repayments of Long-term Debt, Total Repayments of debt Repayments of Long-Term Debt Debt Securities, Held-to-Maturity, Accumulated Unrecognized Gain Gross unrealized gains Other Other Defined Benefit Plan, Other Cost (Credit) Retirement Benefits Retirement Benefits [Text Block] Discount rate Defined Benefit Plan, Assumptions Used Calculating Benefit Obligation, Discount Rate Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Adjustment, Net of Tax, Total Foreign currency translation Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Adjustment, Net of Tax Stock options outstanding Balance as of beginning of period, Outstanding (in shares) Balance as of end of period, Outstanding (in shares) Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Outstanding, Number Real Estate Rationalization [Member] Real estate rationalization [Member] Real estate rationalization. Revolving Credit Facility [Member] Revolving Credit Facility [Member] Willis Towers Watson Public Limited Company [Member] Willis Towers Watson Public Limited Company [Member] Willis Towers Watson public limited company. Intangible assets acquired Finite-Lived Intangible Assets Acquired Retirement Plan Type Retirement Plan Type [Domain] Total current liabilities Liabilities, Current Redeemable Non-controlling interest [Member] Redeemable Noncontrolling Interest [Member] Redeemable noncontrolling interest. Accounts receivable Increase (Decrease) in Accounts Receivable Adjustment to Reconcile Net Income to Cash Provided by (Used in) Operating Activity [Abstract] Adjustments to reconcile net income/(loss) to total net cash from operating activities: Lessee, Operating Lease, Liability, to be Paid, Year Five Operating Lease, 2030 Hedging Designation Hedging Designation [Domain] Revenues from External Customers and Long-Lived Assets [Line Items] Goodwill disposals Goodwill, Written off Related to Sale of Business Unit Effective Income Tax Rate Reconciliation, Disposition of Business, Amount Net tax effect on disposal of operations Net tax effect on disposal of operations Schedule of Change in Fair Value of Level 3 Liabilities Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Table Text Block] Defined Benefit Plan, Accumulated Other Comprehensive (Income) Loss, Prior Service Cost (Credit), before Tax Net prior service loss Fiduciary liabilities Fiduciary Liabilities Current Fiduciary liabilities, current. Employee Status Employee Status [Domain] Employee status. U.S. - Federal [Member] Domestic Tax Authority [Member] Domestic Tax Jurisdiction [Member] Total lease payments Lease Payment Lease payments for both operating lease and finance lease. 3.600% senior notes due 2024 [Member] Senior Notes Due202403600 [Member] Senior notes due 2024, 03600. Deductions Deductions/other movements SEC Schedule, 12-09, Valuation Allowances and Reserves, Deduction Allowance for doubtful accounts [Member] SEC Schedule, 12-09, Allowance, Credit Loss [Member] Book-of-business settlements Book-of-Business Settlements Book-of-Business Settlements. Effective Income Tax Rate Reconciliation [Table] Increases related to tax positions in prior years Unrecognized Tax Benefits, Increase Resulting from Prior Period Tax Positions Debt issuance costs Payments of Debt Issuance Costs Accounts Receivable, after Allowance for Credit Loss, Noncurrent, Total Non-current accounts receivable, net Accounts receivable, net Accounts Receivable, after Allowance for Credit Loss, Noncurrent Time Based Restricted Stock Units RSU [Member] Time based restricted stock units. Time Based Restricted Stock Units [Member] Reduction of non-controlling interests Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Changes, Purchase of Interest by Parent Segment Reconciling Items [Member] Segment Reporting, Reconciling Item, Excluding Corporate Nonsegment [Member] Consolidation Items Consolidation Items [Domain] Payroll and other benefits-related liabilities Payroll and other benefits-related liabilities. Entity Small Business Entity Small Business Designated as Hedging Instrument [Member] Hedging Designation Hedging Designation [Axis] Adjustment of retained earnings Retained Earnings (Accumulated Deficit), Ending Balance Retained Earnings (Accumulated Deficit), Beginning Balance Retained Earnings (Accumulated Deficit), Total Reclassification of tax effects per ASU 2018-02 Retained earnings Retained Earnings (Accumulated Deficit) Defined Benefit Plan, Funded (Unfunded) Status of Plan, Total Funded status at end of year Defined Benefit Plan, Funded (Unfunded) Status of Plan Share-based compensation Deferred Tax Assets, Tax Deferred Expense, Compensation and Benefits, Share-Based Compensation Cost Nature of Operations Nature of Operations [Text Block] Debt Securities, Held-to-Maturity, Allowance for Credit Loss Debt Securities, Held-to-Maturity, Allowance for Credit Loss, Ending Balance Debt Securities, Held-to-Maturity, Allowance for Credit Loss, Beginning Balance Debt Securities, Held-to-Maturity, Allowance for Credit Loss, Total Allowance for credit losses Allowance for credit losses Compensation And Retirement Disclosure [Table] Compensation And Retirement Disclosure [Table] Compensation and retirement disclosure. Effective Income Tax Rate Reconciliation, Cross-Border Tax Effect, Amount Effective Income Tax Rate Reconciliation, Cross-Border Tax Effect, Amount, Total Effect of cross-border tax laws Effect of cross-border tax laws Entity Well-known Seasoned Issuer Entity Well-known Seasoned Issuer Operating loss carryforwards, subject to expiration Deferred Tax Assets, Operating Loss Carryforwards, Subject to Expiration Fair Value, Liability, Recurring Basis, Unobservable Input Reconciliation, Liability, Gain (Loss), Statement of Other Comprehensive Income or Comprehensive Income [Extensible Enumeration] Consulting [Member] Consulting [Member] Consulting. Options, exercises in period, intrinsic value Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Exercises in Period, Intrinsic Value U.K. corporation tax Current Foreign Tax Expense (Benefit) Share-Based Payment Arrangement [Text Block] Share-based Compensation Organization, Consolidation and Presentation of Financial Statements [Abstract] Performance-based Stock Options [Member] Performance Based Stock Options [Member] PerformanceBasedStockOptionsMember Other (loss)/income [Member] Other (Loss)/Income [Member] Other (loss)/income. Leases [Abstract] Repayment of principal and interest outstanding Repayment of principal and interest outstanding. Foreign exchange Property Plant And Equipment Increase Decrease Due To Foreign Exchange Property plant and equipment foreign exchange. Weighted Average Number Diluted Shares Outstanding Adjustment, Total Dilutive effect of potentially issuable shares (shares) Weighted Average Number of Shares Outstanding, Diluted, Adjustment Defined pension and post-retirement benefits [Member] Accumulated Defined Benefit Plans Adjustment Including Portion Attributable to Noncontrolling Interest [Member] Health Wealth Career Segment . Health Wealth Career Segment [Member] HWC [Member] Contract with Customer, Liability, Total Deferred revenue Contract with Customer, Liability Lessee, Lease, Description [Line Items] Amendment Flag Amendment Flag Product and Service Product and Service [Domain] Loss Contingencies [Line Items] Loss Contingencies [Line Items] Other Significant Noncash Transaction, Value of Consideration Given Contingent consideration fair value Share Based Compensation Arrangement by Share-Based Payment Award, Average Expected Volatility Of Peer Companies Share Based Compensation Arrangement by Share-Based Payment Award, Average Expected Volatility Of Peer Companies Average expected volatility of peer companies Income tax expense at U.S. federal tax rate Effective Income Tax Rate Reconciliation at Federal Statutory Income Tax Rate, Amount Fair value of plan assets Fair value of plan assets, beginning of year Fair value of plan assets, end of year Defined Benefit Plan Fair Value Of Plan Assets Liabilities Reconciliation Defined benefit plan fair value of plan assets liabilities reconciliation. Schedule of Held-to-Maturity Securities [Line Items] Delayed Draw Term Loan (DDTL) [Member] Delayed Draw Term Loan [Member] Other Comprehensive Income (Loss), Tax, Portion Attributable to Noncontrolling Interest Other Comprehensive Income (Loss), Tax, Portion Attributable to Noncontrolling Interest, Total Other comprehensive income/(loss), tax Interest on lease liabilities Finance Lease, Interest Expense LIABILITIES AND EQUITY Liabilities and Equity [Abstract] Entity Address, Postal Zip Code Entity Address, Postal Zip Code Accounts Receivable Accounts Receivable [Policy Text Block] Net cash from operating activities Cash Provided by (Used in) Operating Activity, Including Discontinued Operation Debt Instrument, Redemption Price, Percentage Redemption price percentage Debt Securities, Held-to-Maturity, Amortized Cost, before Allowance for Credit Loss, Current Held-to-maturity securities Capitalized software costs Payments to Develop Software Segment Reporting, CODM, Profit (Loss) Measure, How Used, Description Deferred Income Tax Expense (Benefit) for Ireland Deferred income tax expense (benefit) for ireland. Ireland Ireland Shares outstanding [Member] Common Stock [Member] Accumulated Benefit Obligation Defined Benefit Plan, Accumulated Benefit Obligation Employee Service Share-based Compensation, Tax Benefit from Exercise of Stock Options Share-Based Payment Arrangement, Exercise of Option, Tax Benefit Cybersecurity Risk Role of Management [Text Block] Long-Term Debt, Maturity, Year One 2026 Hedging Relationship Hedging Relationship [Domain] Pension benefits assets Assets for Plan Benefits, Defined Benefit Plan Lessee, Operating Lease, Liability, to be Paid, Year Three Operating Lease, 2028 Schedule of Effect of Significant Unobservable Inputs, Changes in Plan Assets Schedule of Effect of Significant Unobservable Inputs, Changes in Plan Assets [Table Text Block] Accumulated Depreciation, Depletion and Amortization, Property, Plant, and Equipment, Ending Balance Accumulated Depreciation, Depletion and Amortization, Property, Plant, and Equipment, Beginning Balance Accumulated Depreciation, Depletion and Amortization, Property, Plant, and Equipment, Total Depreciation: at beginning of period Depreciation: at end of period Accumulated Depreciation, Depletion and Amortization, Property, Plant, and Equipment Unallocated, net Other Operating Income (Expense), Net Proceeds from (Payments to) Noncontrolling Interests, Total Acquisitions of and dividends paid to non-controlling interests Proceeds from (Payments to) Noncontrolling Interests Lease Liability Payments Due Year Two Amount of lessee's undiscounted obligation for lease payments for operating lease and finance lease, due in second fiscal year following latest fiscal year. Total Lease, 2027 Income Tax Paid, by Individual Jurisdiction [Line Items] Effective interest rate (as a percent) Debt Instrument, Interest Rate, Effective Percentage Portion at Fair Value Measurement [Member] [Default] Fair Value Disclosure Item Amounts [Default] Portion at Fair Value Measurement [Member] Entity Address, Address Line One Entity Address, Address Line One Deferred tax liabilities Deferred Tax Liabilities, Gross Deferred tax liabilities Deferred tax liabilities Deferred tax liabilities Intangible asset disposals Finite Lived Intangible Assets Disposed Finite-lived intangible assets disposed. Fair Value Hierarchy and NAV Fair Value Hierarchy and NAV [Axis] Earnings Per Share [Abstract] EARNINGS/(LOSS) PER SHARE Income Taxes Income Tax, Policy [Policy Text Block] HCB [Member] Human Capital And Benefits [Member] Human capital and benefits. Cybersecurity Risk Materially Affected or Reasonably Likely to Materially Affect Registrant [Flag] Supplemental disclosures of cash flow information: Supplemental Cash Flow Information [Abstract] Foreign Currency Foreign Currency Transactions and Translations Policy [Policy Text Block] Derivative financial instruments Derivative Asset Derivative asset, fair value Derivative Asset, fair value Goodwill and Other Intangible Assets Goodwill and Intangible Assets Disclosure [Text Block] Foreign currency translation Adjustments To Additional Paid In Capital Foreign Currency Translation Gain Loss Adjustments to additional paid in capital, foreign currency translation gain (loss). Defined Benefit Plan, Expected Future Benefit Payment, Year Four 2029 Balance Sheet Location Statement of Financial Position Location, Balance [Axis] Tax Year Two Thousand Twenty Six Through Two Thousand Forty Five [Member] Tax year two thousand twenty six through two thousand forty five. Tax Year 2026 Through 2045 [Member] Schedule of Assets and Liabilities Whose Carrying Values Differ From the Fair Value and are Not Measured on a Recurring Basis Fair Value Measurements, Nonrecurring [Table Text Block] Lessee Lease Liabilities Payments Due Abstract Leases Liabilities Due [Abstract] Lessee Lease Liabilities Payments Due [Abstract] Right-of-use assets Operating Lease, Right-of-Use Asset Finance Lease, Interest Finance Lease, Liability, Undiscounted Excess Amount Defined Benefit Plan, Plan Assets, Category Defined Benefit Plan, Plan Assets, Category [Domain] Gross deferred tax assets Deferred Tax Assets, Gross Cybersecurity Risk Board Committee or Subcommittee Responsible for Oversight [Text Block] Balance Sheet Date Balance Sheet Date [Domain] Balance sheet date. Net Income (Loss) Attributable to Noncontrolling Interest, Total Income attributable to non-controlling interests Net Income (Loss) Attributable to Noncontrolling Interest Business Combination, Contingent Consideration [Line Items] Payments to Acquire Debt Securities, Available-for-Sale Net purchases of available-for-sale securities Disposal Group, Including Discontinued Operation, Revenue Revenue Revolving 1.25 Billion Dollar Credit Facility [Member] Revolving125 Billion Dollar Credit Facility [Member] Revolving 1.25 billion dollar credit facility. Document Type Document Type Goodwill and Other Intangible Assets Goodwill and Intangible Assets, Policy [Policy Text Block] Income Taxes Paid, Net, Total Cash payments for income taxes, net Income Taxes Paid, Net Cash paid for income taxes, net of refunds Western Europe [Member] Western Europe. Europe [Member] Going Concern Going Concern Policy [Text Block] Going concern. Entity Central Index Key Entity Central Index Key Operating lease right-of-use assets Deferred Tax Liabilities Operating Lease Right Of Use Assets Deferred tax liabilities operating lease right of use assets. Operating lease right-of-use assets Cybersecurity Risk Process for Informing Board Committee or Subcommittee Responsible for Oversight [Text Block] Realized Gain (Loss), Foreign Currency Transaction, before Tax Foreign exchange (loss)/gain Nontrade Receivables, Current Nontrade Receivables, Current, Total Note receivable Cash, Cash Equivalent, Restricted Cash, and Restricted Cash Equivalent, Period Increase (Decrease), Excluding Exchange Rate Effect, Including Discontinued Operation INCREASE/(DECREASE) IN CASH, CASH EQUIVALENTS AND RESTRICTED CASH Increase in cash, cash equivalents and other restricted cash Subsequent Event Type [Domain] Foreign exchange Valuation Allowances And Reserves Foreign Exchange Differences Valuation allowances and reserves foreign exchange differences. Operating Activities [Axis] Antidilutive securities excluded from computation of earnings per share Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount Plan amendments Defined Benefit Plan, Benefit Obligation, Increase (Decrease) for Plan Amendment Shares repurchased (in shares) Stock Repurchased and Retired During Period, Shares Switzerland SWITZERLAND Ordinary shares, nominal value Common Stock, Par or Stated Value Per Share Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent Net other comprehensive income/(loss) Term Loan Notes Payable [Member] Notes Payable to Banks [Member] Operating Lease, Right-of-Use Asset, Periodic Reduction Non-cash lease expense Bank Base Rate [Member] Base Rate [Member] Goodwill [Line Items] Goodwill [Line Items] Newfront [Member] Newfront member. Newfront Increase (Decrease) in Other Operating Liabilities, Total Other liabilities Increase (Decrease) in Other Operating Liabilities Retirement Plan Sponsor Location Retirement Plan Sponsor Location [Domain] Foreign currency changes Foreign currency changes Defined Benefit Plan, Benefit Obligation, Foreign Currency Translation Gain (Loss) Foreign Tax Jurisdiction, Other [Member] Other Foreign Jurisdictions [Member] Noncash or Part Noncash Divestiture, Amount of Consideration Received Non-cash proceeds from other disposal Total WTW shareholders' equity [Member] Parent [Member] Document Financial Statement Error Correction [Flag] Document Financial Statement Error Correction [Flag] Other legislation Other Legislation [Policy Text Block] Other Legislation Other Sundry Liabilities, Noncurrent Other non-current liabilities Rollforward of Liability Associated with Cash-based Charges Rollforward of liability associated with cash-based charges [Table Text Block] Rollforward of liability associated with cash-based charges. Exercised, Outstanding (in shares) Exercised, Outstanding (in shares) Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Exercises in Period Not Issued [Member] Not Issued. Debt Disclosure [Abstract] Germany [Member] GERMANY Derivative instruments Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), after Reclassification and Tax Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), after Reclassification and Tax, Total (Loss)/gain recognized in OCL (effective element) Foreign currency translation [Member] Accumulated Foreign Currency Adjustment Attributable to Parent [Member] Derivative [Table] Derivative [Table] U.S. State Capital [Member] U.S. state capital. U.S. State Capital [Member] Decreases related to settlements Unrecognized Tax Benefits, Decrease Resulting from Settlements with Taxing Authorities Supplemental Cash Flow Elements [Abstract] Fair Value [Member] Estimate of Fair Value Measurement [Member] Hedge funds [Member] Hedge Funds [Member] Mutual funds / exchange traded funds Marketable Securities Marketable Securities, Total Derivative, notional amount Derivative, Notional Amount Ownership Ownership [Domain] Current Fiscal Year End Date Current Fiscal Year End Date Actual return on plan assets Defined Benefit Plan, Plan Assets, Increase (Decrease) for Actual Return (Loss) Debt Instrument [Table] Schedule of Long-Term Debt Instruments [Table] Schedule of Other Non-current Liabilities Other Noncurrent Liabilities [Table Text Block] Investment in associates Investments in and Advance to Affiliates, Subsidiaries, Associates, and Joint Ventures Investments in and Advance to Affiliates, Subsidiaries, Associates, and Joint Ventures, Total Restricted Cash and Cash Equivalents [Axis] Other Cost and Expense, Operating, Total Other operating expenses Other Cost and Expense, Operating Willis Re [Member] Willis Re [Member] Willis Re. Willis Re Remaining Number of Reporting Units Remaining number of reporting units. Remaining number of reporting units Client relationships [Member] Customer Relationships [Member] Entity Address, State or Province Entity Address, State or Province Deferred contract costs Capitalized Contract Cost, Net, Current Liability, Pension and Other Postretirement and Postemployment Benefits, Current Accrued 401(k) contributions Capitalized Contract Cost, Foreign Exchange Translation Gain (Loss) Capitalized Contract Cost Foreign Exchange Translation Gain Loss Capitalized Contract Cost, Foreign Exchange Translation Gain (Loss) Balance (shares) Balance (shares) Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Nonvested, Number Number of shares non vested Prepayments and accrued income Prepaid Expense And Accrued Revenue Receivable Noncurrent Prepaid expense and accrued revenue receivable noncurrent. Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Share-Based Liabilities Paid Cash payments made on stock awards Number of grantees benefited from modifications Share-Based Payment Arrangement, Plan Modification, Number of Grantees Affected Comprehensive Income (Loss), Net of Tax, Attributable to Parent Comprehensive income/(loss) attributable to WTW Dilutive effect of potentially issuable shares Dilutive Securities Effect On Basic Earnings Per Share Continuing Operations Dilutive securities effect on basic earnings per share continuing operations. Schedule of Assumptions Used Defined Benefit Plan, Assumptions [Table Text Block] Geographical Geographical [Axis] Noncontrolling Interest, Increase from Business Combination Additional non-controlling interests Contract with Customer, Liability, Revenue Recognized Contract with Customer, Liability, Revenue Recognized Fiduciary assets Funds Held for Clients Fiduciary Assets and Liabilities Fiduciary Assets And Fiduciary Liabilities Policy [Text Block] Disclosure of accounting policy for fiduciary assets and liabilities i.e. balances that have been or are due to be collected or remitted to insurers and/or insured in the Company's capacity as an insurance broker or agent. Marketable Securities, Current Available-for-sale securities Stockholders' Equity Attributable to Noncontrolling Interest, Ending Balance Stockholders' Equity Attributable to Noncontrolling Interest, Beginning Balance Stockholders' Equity Attributable to Noncontrolling Interest, Total Non-controlling interests Equity, Attributable to Noncontrolling Interest Deferred compensation plan assets Deferred Compensation Plan Assets Current Deferred compensation plan assets current. Effective Income Tax Rate Reconciliation, State and Local Income Taxes, Amount Impact of U.S. state and local taxes (net of federal taxes) Deferred and long-term compensation plan liabilities Deferred Compensation Liability, Classified, Noncurrent, Total Deferred Compensation Liability, Classified, Noncurrent Finance Lease, Thereafter Finance Lease, Liability, to be Paid, after Year Five Schedule of Deferred Tax Assets and Liabilities [Table Text Block] Significant Components of Deferred Income Tax Assets and Liabilities and Their Balance Sheet Classifications Total interest and other income Interest and other income Interest and Other Income Termination of Proposed Combination with AON Plc [Member] Termination Of Proposed Combination With A O N Plc [Member] Termination of proposed combination with AON Plc. Other Comprehensive Income (Loss), Net of Tax [Abstract] Other comprehensive income/(loss), net of tax: Performance-based [Member] Performance-Based Stock Units [Member] Performance Shares [Member] Deferred tax assets Deferred Income Tax Assets, Net Net deferred tax assets/(liabilities) PRW [Member] Other Postretirement Benefits Plan [Member] Subsequent Event [Member] Subsequent Event [Member] Schedule of Maturity of Operating and Finance Leases Liabilities Lessee Operating And Finance Lease Liability Maturity Table [Text Block] Tabular disclosure of undiscounted cash flows of lessee's operating lease liability and finance lease liability. includes, but is not limited to, reconciliation of undiscounted cash flows to lease liabilities recognized in statement of financial position. Property, Plant and Equipment [Abstract] Debt Securities, Held-to-Maturity, Amortized Cost, before Allowance for Credit Loss, Noncurrent Held-to-maturity securities Finite Lived Intangible Assets Acquired As Part Of Business Combination [Table] Business Combination, Intangible Asset, Acquired, Finite-Lived [Table] Billed Contracts Receivable Billed Receivable, Current Total other non-current assets Other non-current assets Other Assets, Noncurrent Revenue [Member] Revenue [Member] Revenue member. Termination payment Gain (Loss) on Contract Termination Deferred Revenue Arrangement Type [Axis] Revenue: Segment Reconciliation [Abstract] Antidilutive Securities Antidilutive Securities [Axis] Operating Loss Carryforwards [Line Items] Operating Loss Carryforwards [Line Items] Senior notes issued Proceeds from Issuance of Senior Long-Term Debt Basis of Presentation, Significant Accounting Policies and Recent Accounting Pronouncements Basis of Presentation and Significant Accounting Policies [Text Block] Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Vested in Period, Fair Value Fair value of stock issued Other [Member] Product and Service, Other [Member] Contingent and deferred consideration on acquisitions Business Combination Contingent Consideration Liability And Deferred Consideration Current Business combination contingent consideration liability and deferred consideration current. State and Local [Member] State and Local Jurisdiction [Member] Insurance contracts [Member] Insurance Contracts [Member] Insurance contracts. Total [Member] AOCI Attributable to Parent [Member] AOCI Attributable to Parent [Member] Derivative Liability, Total Derivative financial instruments Derivative Liability Derivative liability, fair value Finite-Lived Intangible Assets, Major Class Name Finite-Lived Intangible Assets, Major Class Name [Domain] Senior notes due 202704650 [Member]. Senior Notes Due 202704650 [Member] 4.650% senior notes due 2027 [Member] Treasury shares Treasury Stock, Common, Shares Goodwill, Impairment Loss Goodwill impairment Impairment Impairment Goodwill disposals Thereafter Finite-Lived Intangible Asset, Expected Amortization, after Year Five Cash and Cash Equivalents [Domain] Increase (Decrease) in Stockholders' Equity [Roll Forward] Increase (Decrease) in Stockholders' Equity [Roll Forward] Number of employees employed Entity Number of Employees Debt Securities, Held-to-Maturity [Table] Other comprehensive income/(loss), before tax Other Comprehensive Income (Loss), before Tax, Portion Attributable to Noncontrolling Interest Other Comprehensive Income (Loss), before Tax, Portion Attributable to Noncontrolling Interest, Total Other comprehensive income/(loss), before tax Contingent consideration fair value Business Combination, Consideration Transferred Business Combination, Consideration Transferred, Total Deferred Income Tax Expense (Benefit), Continuing Operations [Abstract] Deferred tax (expense)/benefit: Disposal Groups, Including Discontinued Operations [Table Text Block] Schedule of Selected Financial Information Related to Operations of TRANZACT Maturity date Debt Instrument, Maturity Date Minimum [Member] Minimum [Member] Granted, Weighted Average Grant Date Fair Value (in dollars per share) Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Grants in Period, Weighted Average Grant Date Fair Value Weighted-average grant date fair values Financial Instrument [Axis] Broking [Member] Broking [Member] Broking. Earnout receivable in cash in 2025 Earnout Receivable In Cash Earnout receivable in cash not recognized as an asset on balance sheet. Real estate [Member] Real Estate [Member] Aon Plc [Member] Aon Plc [Member] Aon plc. Other Comprehensive Income (Loss), Tax, Total Other Comprehensive Income (Loss), Tax Other comprehensive income/(loss), tax Reconciliation Of Operating Profit Loss From Segments To Consolidated [Table] Reconciliation of Operating Profit (Loss) from Segments to Consolidated [Table] Effective Income Tax Rate Reconciliation, GILTI, Amount Global Intangible Low-Taxed Income (GILTI) Global Intangible Low-Taxed Income (GILTI) Quarterly Financial Data (Unaudited) Quarterly Financial Information [Text Block] Amortization of Intangible Assets, Total Amortization Amortization Amortization of Intangible Assets Level 3 [Member] Fair Value, Inputs, Level 3 [Member] Nonrecurring [Member] Fair Value, Nonrecurring [Member] Liabilities: Liabilities, Fair Value Disclosure [Abstract] Segment Reporting [Abstract] Cost of tangible assets, net of related depreciation Deferred Tax Liabilities, Property, Plant and Equipment Cost of tangible assets, net of related depreciation Schedule of Assets and Liabilities Measured at Fair Value on Recurring Basis Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis [Table Text Block] Tax Period Tax Period [Domain] Trinity Acquisition plc [Member] Trinity Acquisition Plc [Member] Trinity Acquisition plc. Restructuring Costs Restructuring and Related Activities Disclosure [Text Block] Interest on income taxes accrued Unrecognized Tax Benefits, Interest on Income Taxes Accrued Shares repurchased Stock Repurchased and Retired During Period, Value Other Current Liabilities [Table Text Block] Schedule of Other Current Liabilities Portion of Revenue Portion Of Revenue Portion Of Revenue Deferred compensation plans Deferred Compensation Plan Assets Deferred compensation plan assets Effect of foreign exchange and other differences Effective Income Tax Rate Reconciliation Effect Of Foreign Exchange And Other Differences Effective income tax rate reconciliation, effect of foreign exchange and other differences. Equity, beginning balance (in shares) Equity, ending balance (in shares) Shares, Outstanding Sublease income Sublease Income Accounts receivable, net Accounts receivable, net Accounts Receivable, after Allowance for Credit Loss, Current Contract with Customer, Asset and Liability Schedule of Accounts, Notes, Loans and Financing Receivable [Table Text Block] Other Income Other income Tax Credit Carryforward [Table] Tax Credit Carryforward [Table] Income Tax Paid, by Individual Jurisdiction [Abstract] COMMITMENTS AND CONTINGENCIES Commitments and Contingencies Net book value Property, Plant, and Equipment and Finance Lease Right-of-Use Asset, after Accumulated Depreciation and Amortization Leases Lessee, Leases [Policy Text Block] Deferred compensation Deferred Tax Assets, Tax Deferred Expense, Compensation and Benefits, Total Deferred Tax Assets, Tax Deferred Expense, Compensation and Benefits SEC Schedule, 12-09, Valuation Allowances and Reserves SEC Schedule, 12-09, Valuation Allowances and Reserves [Domain] Service cost Defined Benefit Plan, Service Cost Schedule of Cash Paid in the Measurement of Lease Liabilities Schedule Of Cash Paid For Amount In Measurement Of Lease Liabilities Table [Text Block] Schedule of cash paid for amount in the measurement of lease liabilities. Grant date fair value,per share Balance, Weighted Average Grant Date Fair Value (in dollars per share) Balance, Weighted Average Grant Date Fair Value (in dollars per share) Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value Benefits Delivery and Administration Reporting Unit [Member] Benefits delivery and administration reporting unit. Benefits, Delivery and Administration Reporting Unit [Member] Shares Issued, Shares, Share-based Payment Arrangement, after Forfeiture, Total Issuance of shares under employee stock compensation plans (in shares) Shares Issued, Shares, Share-Based Payment Arrangement, after Forfeiture Provision for doubtful receivables from clients Accounts Receivable, Credit Loss Expense (Reversal) Operating Lease, Liability, Total Operating Lease, Total lease liabilities Operating Lease, Liability Acquisition accounting adjustment Goodwill, Measurement Period Adjustment Deferred Compensation Liability, Current, Total Deferred compensation plan liabilities Deferred Compensation Liability, Current Auditor Firm ID Debt Instrument, Basis Spread on Variable Rate Interest rate spread Benefit From Income Taxes [Member] Benefit from income taxes. Benefit From Income Taxes [Member] Components of Goodwill Schedule of Goodwill [Table Text Block] Cash flows from operating activities: Cash Flow, Operating Activities, Lessee [Abstract] Net tax effect on intra-group items Effective Income Tax Rate Reconciliation, Deduction, Other, Amount Other restricted cash (included in prepaids and other current assets) Restricted cash Restricted Cash, Current Contingent consideration [Member] Obligations [Member] Average remaining service period Defined Benefit Plan Average Remaining Service Period Defined benefit plan, average remaining service period. Concentration Risk Benchmark [Axis] Long-Term Debt, Maturity, Year Two 2027 Non Rule 10b51 Arr Modified Flag Non rule 10b51 arr modified flag. Finance Lease, Current lease liabilities Finance Lease, Liability, Current Lessee, Lease, Description [Table] Finance Leases, Weighted-average discount rate Finance Lease, Weighted Average Discount Rate, Percent Effective Income Tax Rate Reconciliation, Change in Deferred Tax Assets Valuation Allowance, Percent Changes in valuation allowance, Percentage Changes in valuation allowance, Percentage Contributions to investments in associates Payments to Acquire Equity Method Investments Further investments into business Net income NET (LOSS)/INCOME NET INCOME/(LOSS) NET INCOME/(LOSS) Increase (Decrease) In Deferred Income Tax Assets and Liabilities Increase decrease in deferred income tax assets and liabilities. Net change in deferred income tax assets and liabilities Tax Credit Carryforward [Line Items] Tax Credit Carryforward [Line Items] Debt Securities, Held-to-Maturity, Amortized Cost, before Allowance for Credit Loss Debt Securities, Held-to-Maturity, Amortized Cost, before Allowance for Credit Loss, Total Amortized cost basis Other [Member] Notes Payable, Other Payables [Member] Settlement Other Comprehensive Income (Loss), Defined Benefit Plan, Settlement and Curtailment Gain (Loss), before Tax Non-Fiduciary [Member] Non-Fiduciary [Member] Non-Fiduciary. Long-term Debt, Type Long-Term Debt, Type [Domain] Cybersecurity Risk Management Positions or Committees Responsible [Text Block] Loss Contingencies [Table] Loss Contingencies [Table] Weighted Average Number of Shares Outstanding, Basic, Total Basic weighted-average number of shares outstanding (shares) Weighted Average Number of Shares Outstanding, Basic Goodwill acquired Goodwill, Acquired During Period Nonqualified Plan [Member] Restrictions on Cash and Cash Equivalents [Table] Schedule of Assumptions Schedule Of Share Based Payment Award Restricted Stock Units Valuation Assumptions Table [Text Block] Schedule​ of share ​based ​payment​ award​ restricted stock units valuation ​assumptions​. Change in Plan Assets Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward] Interest income Interest Income, Operating and Nonoperating Interest Income, Operating and Nonoperating, Total 4.400% senior notes due 2026 [Member] Senior Notes Due202604400 [Member] Senior notes due 2026, 04400. 4.625% senior notes due 2023 [Member] Senior Notes Due202304625 [Member] Senior notes due 2023, 04625. Senior Notes Due 203605150 [Member] Senior notes due 2036, 05150. 5.150% senior notes due 2036 [Member] Incremental compensation cost recognized over service periods Share-Based Payment Arrangement, Plan Modification, Incremental Cost Schedule of Effective Income Tax Rate Reconciliation [Table Text Block] Reconciliation Between US Federal Income Taxes at the Statutory Rate and the Company's Provision for Income Taxes on Continuing Operations Schedule Of Share Based Compensation Arrangements By Share Based Payment Award [Table] Schedule of Share-Based Compensation Arrangements by Share-Based Payment Award [Table] Certificates of Deposit and Term Deposits [Member] Certificates of Deposit And Term Deposits [Member] Certificates of deposit and term deposits. Segments Segments [Axis] Long-Lived Tangible Asset Long-Lived Tangible Asset [Domain] Transaction and integration, net Business Combination Integration Related Transaction Costs Business combination integration related transaction costs. Transaction and transformation Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Net of Forfeitures, Total Options granted Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Grants in Period, Net of Forfeitures Cybersecurity Risk Process for Informing Management or Committees Responsible [Text Block] Other jurisdictions Deferred Other Jurisdictions Tax Expense Benefit Deferred other jurisdictions tax expense benefit. Finance Lease, Right-of-Use Asset, Statement of Financial Position [Extensible Enumeration] Subsequent Events Subsequent Events [Text Block] Other Foreign Plans [Member] Other Foreign Plans [Member] Other foreign plans. Pension and Other Postretirement Benefits Expense (Reversal of Expense), Noncash, Total Pension and Other Postretirement Benefits Expense (Reversal of Expense), Noncash Net periodic cost of/(credit for) defined benefit pension plans Foreign tax credits, Percentage Effective Income Tax Rate Reconciliation, Tax Credit, Percent Effective Income Tax Rate Reconciliation, Tax Credit, Percent, Total Foreign tax credits, Percentage Borrowings Total Long-Term Debt Deferred Tax Asset, Interest Carryforward Interest carryforwards Cash, Ending Balance Cash, Beginning Balance Unencumbered and available cash balance required Cash Debt Instrument, Interest Rate Terms Debt Instrument, Interest Rate Terms Variable Rate Variable Rate [Domain] Actuarial (gains)/losses Defined Benefit Plan, Benefit Obligation, Actuarial Gain (Loss) Actuarial losses/(gains) Changes in valuation allowances Effective Income Tax Rate Reconciliation, Change in Deferred Tax Assets Valuation Allowance, Amount Total WTW shareholders' equity Stockholders' equity attributable to parent, beginning balance Stockholders' equity attributable to parent, ending balance Equity, Attributable to Parent Curtailments Curtailments Defined Benefit Plan, Benefit Obligation, (Increase) Decrease for Curtailment Preference shares, nominal value (USD per share) Preferred Stock, Par or Stated Value Per Share Reimbursable expenses and other Reimbursable Expenses And Other Reimbursable expenses and other. Schedule of Debt Interest Expense Interest Income and Interest Expense Disclosure [Table Text Block] Basis of Presentation Basis of Accounting, Policy [Policy Text Block] Accrued expenses not currently deductible Deferred Tax Assets, Tax Deferred Expense, Reserves and Accruals, Other Statement of Stockholders' Equity [Abstract] Percentage of non elective contribution of eligible earnings Defined Contribution Plan Employer Contribution Non Elective Percent Defined contribution plan employer contribution non elective percent. Defined Benefit Plan, Change in Fair Value of Plan Assets, Level 3 Reconciliation [Roll Forward] Defined Benefit Plan, Change in Fair Value of Plan Assets, Level 3 Reconciliation [Roll Forward] Debt Securities, Held-to-Maturity, Accumulated Unrecognized Loss Gross unrealized losses Gross unrealized losses Type of Restructuring Type of Restructuring [Domain] Use of Estimates Use of Estimates, Policy [Policy Text Block] Cumulative costs. Cumulative Costs [Member] Other Comprehensive Income (Loss), Defined Benefit Plan, Gain (Loss) Arising During Period, before Tax Net actuarial loss/(gain) Other fixed income [Member] Fixed Income Securities [Member] Treasury Stock, Common [Member] Treasury Stock, Common [Member] Long-Term Debt, Maturity, Year Five 2030 Defined Benefit Plan Disclosure [Line Items] Defined Benefit Plan Disclosure [Line Items] Leasehold Improvements [Member] Leasehold Improvements [Member] Finance leases Property, Plant, and Equipment and Finance Lease Right-of-Use Asset, before Accumulated Depreciation and Amortization Foreign Currency Transaction Gain (Loss), before Tax, Total Gain (Loss), Foreign Currency Transaction, before Tax Non-cash foreign exchange loss/(gain) Other comprehensive income/(loss) before reclassifications OCI, before Reclassifications, Net of Tax, Attributable to Parent Entity Address, Address Line Two Entity Address, Address Line Two Fair Value Measurements Fair Value Disclosures [Text Block] Non-cash revaluation gain related to acquisition. Non-cash Revaluation Gain Related to Acquisition [Member] 4.125% Senior Notes Due 2016 [Member] Senior Notes Due2016 [Member] Senior Notes Due 2016 [Member] Payments to Acquire Held-to-Maturity Securities Net purchases of held-to-maturity securities Debt securities UNITED STATES [Member] United States [Member] UNITED STATES Defined pension and post-retirement benefit costs [Member] Accumulated Defined Benefit Plans Adjustment Attributable to Parent [Member] Non-controlling interests [Member] Noncontrolling Interest [Member] Debt Instrument, Name Debt Instrument, Name [Domain] Other current assets Other Assets, Current Fair Value Inputs, Discount Rate [Member] Measurement Input, Discount Rate [Member] Derivatives and investments Derivatives And Investments Current Derivatives and investments current. Income (Loss) from Equity Method Investments, Total Interest in earnings of associates and other investments Income (Loss) from Equity Method Investments Interest in earnings of associates, net of tax Long-Term Debt, Maturity, Year Four 2029 Acquired Finite Lived Intangible Assets [Line Items] Intangible Asset, Acquired, Finite-Lived [Line Items] Schedule of Unrecognized Tax Benefits Roll Forward [Table Text Block] Reconciliation of the Beginning and Ending Amounts of Unrecognized Tax Benefits Derivative Instruments and Hedging Activities Disclosure [Abstract] Segment Reporting, CODM, Individual Title and Position or Group Name [Extensible Enumeration] Net (payments)/proceeds from fiduciary funds held for clients Net Payments Proceeds from Fiduciary Funds Held for Clients Net (payments)/proceeds from fiduciary funds held for clients. Net proceeds/(payments) from fiduciary funds held for clients Income (Loss) from Discontinued Operations and Disposal of Discontinued Operations, Net of Tax, Per Basic Share, Total Income (Loss) from Discontinued Operations and Disposal of Discontinued Operations, Net of Tax, Per Basic Share Basic earnings/(loss) per share Segment Reporting, Other Segment Item, Amount Other segment expenses Plan Name Plan Name [Domain] Software [Member] Software and Software Development Costs [Member] Increase (Decrease) in Other Operating Assets, Total Other assets Increase (Decrease) in Other Operating Assets Payments Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Settlements Interest Expense, Total Interest expense Interest expense Interest Expense, Operating and Nonoperating Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis] Entity [Domain] Entity Building [Member] Buildings [Member] Credit Facility Credit Facility [Axis] Equity ownership voting percentage Equity Method Investment, Ownership Percentage Cybersecurity Risk Materially Affected or Reasonably Likely to Materially Affect Registrant [Text Block] Termination Agreement [Member] Termination Agreement Contract Termination [Member] U.S. state and local taxes Current State and Local Tax Expense (Benefit) Schedule of Expected Benefit Payments Schedule of Expected Benefit Payments [Table Text Block] Cybersecurity Risk Management Expertise of Management Responsible [Text Block] Finance Lease, Liability, to be Paid, Year One Finance Lease, 2026 Debt securities [Member] Debt Securities [Member] Trident V Parallel Fund [Member] Trident V Parallel Fund [Member] Trident V parallel fund. 6.125% senior notes due 2043 [Member] Senior Notes Due204306125 [Member] Senior notes due 2043, 06125. Expected future employer contributions, next fiscal year Defined Benefit Plan, Expected Future Employer Contributions, Next Fiscal Year Tax Period Tax Period [Axis] Other Non-current Assets [Member] Other Noncurrent Assets [Member] Treasury shares, at cost, 17,519 in 2022 Treasury Stock, Value, Ending Balance Treasury Stock, Value, Beginning Balance Treasury Stock, Value, Total Treasury Stock, Value Operating Leases [Abstract] Lessee, Operating Lease, Liability, to be Paid, Fiscal Year Maturity [Abstract] Restructuring Plan [Axis] Related and Nonrelated Parties [Axis] Effective Income Tax Rate Reconciliation, Other Adjustments, Amount Other items, net Senior Notes Due 2031, 04.504 [Member] Senior Notes Due 2031, 04.504. 4.504% senior notes due 2031 [Member] Foreign Tax Authority [Member] Foreign Tax Jurisdiction [Member] Pension Plan [Member] Pension Plan [Member] Fixed Assets Property, Plant and Equipment, Policy [Policy Text Block] Disposal Group Name Disposal Group Name [Domain] Senior Unsecured Long Term Debt [Member] Senior Unsecured Long Term Debt [Member] Senior unsecured long term debt. Foreign exchange contracts [Member] Foreign Exchange Contract [Member] Entity Address, City or Town Entity Address, City or Town Financing Receivable, before Allowance for Credit Loss, Current Short-term note receivable Undistributed earnings Undistributed Earnings, Basic Undistributed Earnings, Basic, Total Operating Loss Carryforwards, Valuation Allowance, Total Operating loss carryforwards, valuation allowance Operating Loss Carryforwards, Valuation Allowance Number of reportable segments Number of Reportable Segments Security Exchange Name Security Exchange Name Credit Facility Credit Facility [Domain] Europe [Member] Europe [Member] Fair value of deferred and contingent consideration related to acquisitions Non Cash Or Part Non Cash Acquisition Fair Value Of Deferred And Contingent Consideration Noncash or part Noncash acquisition fair value of deferred and contingent consideration Other Defined Benefit Plan, Benefit Obligation, Increase (Decrease) for Other Change Effective Income Tax Rate Reconciliation, Other Adjustments, Percent Other adjustments, Percentage Gallagher [Member] Gallagher [Member] Gallagher. Property, Plant and Equipment, Gross, Total Cost: at beginning of period Cost: at end of period Property, Plant and Equipment, Gross Current tax expense: Current Income Tax Expense (Benefit), Continuing Operations [Abstract] Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest (LOSS)/ INCOME FROM CONTINUING OPERATIONS BEFORE INCOME TAXES INCOME FROM CONTINUING OPERATIONS BEFORE INCOME TAXES AND INTEREST IN EARNINGS OF ASSOCIATES INCOME FROM OPERATIONS BEFORE INCOME TAXES AND INTEREST IN EARNINGS OF ASSOCIATES Ordinary shares and APIC [Member] Common Stock Including Additional Paid in Capital [Member] Concentration Risk Type [Domain] Finance Lease, Liability, to be Paid, Year Five Finance Lease, 2030 Rule 10b51 Arr Modified Flag Rule 10b51arr modified flag. Significant Accounting Policies And Recent Accounting Pronouncements [Line Items] Significant Accounting Policies And Recent Accounting Pronouncements [Line Items] Significant accounting policies and recent accounting pronouncements. Measurement Input Type Measurement Input Type [Domain] Antidilutive Securities, Name Antidilutive Securities, Name [Domain] Retirement Plan Sponsor Location Retirement Plan Sponsor Location [Axis] Cushon Cushon [Member] Cushon member. Effective Income Tax Rate Reconciliation, Foreign Income Tax Rate Differential, Percent Statutory tax rate difference, Percentage Statutory tax rate difference, Percentage Income (Loss) from Discontinued Operations and Disposal of Discontinued Operations, Net of Tax, Per Diluted Share Diluted earnings/(loss) per share Value of remaining settlement amount Value of Remaining Settlement Amount Value of remaining settlement amount. CRB [Member] Corporate Risk And Broking [Member] Corporate risk and broking. Number of countries in which entity operates (more than 140) Number of Countries in which Entity Operates Divested Businesses Divested Businesses [Member] Divested Businesses [Member] Cash, cash equivalents and restricted cash Total cash, cash equivalents and restricted cash CASH, CASH EQUIVALENTS AND RESTRICTED CASH, BEGINNING OF YEAR CASH, CASH EQUIVALENTS AND RESTRICTED CASH, END OF YEAR Cash, Cash Equivalent, Restricted Cash, and Restricted Cash Equivalent, Continuing Operation BERMUDA Bermuda [Member] Cash payments for interest Interest Paid, Excluding Capitalized Interest, Operating Activity Derivative instruments [Member] Accumulated Gain (Loss), Cash Flow Hedge, Including Noncontrolling Interest [Member] Measurement Basis Measurement Basis [Axis] Statistical Measurement Statistical Measurement [Domain] Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net, Total Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net Gain/(loss) recognized in income Foreign exchange Accumulated Depreciation Depletion And Amortization Foreign Exchange Accumulated depreciation depletion and amortization foreign exchange. Movement in Accumulated Depreciation, Depletion and Amortization, Property, Plant and Equipment [Roll Forward] Movement in Accumulated Depreciation, Depletion and Amortization, Property, Plant and Equipment [Roll Forward] Total current assets Assets, Current Share-based compensation Share-Based Payment Arrangement, Expense Increase in salary maximum amount Maximum Annual Salary Amount Maximum annual salary amount. Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Table Text Block] Fiduciary Assets [Member] Fiduciary assets. Document Period End Date Document Period End Date Other Income and Expenses [Abstract] Fair Value Hierarchy and NAV Fair Value Hierarchy and NAV [Domain] Defined contribution plan expenses Defined Contribution Plan, Cost ICFR Auditor Attestation Flag ICFR Auditor Attestation Flag Benefits paid Defined Benefit Plan, Benefit Obligation, Benefits Paid Other non-current assets Other Assets, Miscellaneous, Noncurrent Fair value of plan assets at end of year Defined Benefit Plan, Pension Plan with Projected Benefit Obligation in Excess of Plan Assets, Plan Assets Finance Lease, Liability, Noncurrent, Statement of Financial Position [Extensible Enumeration] Outsourced administration [Member] Outsourced Administration [Member] Outsourced administration. Expected life Acquired Finite-Lived Intangible Assets, Weighted Average Useful Life Statement of Financial Position [Abstract] Restricted share units [Member] Restricted Stock Units [Member] Restricted Stock Units (RSUs) [Member] Revenue Remaining Performance Obligation Expected Timing Of Satisfaction [Line Items] Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items] Loss Contingency Nature Loss Contingency Nature [Axis] Line of Credit [Member] Line of Credit [Member] Loss Contingency, Nature Loss Contingency, Nature [Domain] Disposal Group, Not Discontinued Operation, Gain (Loss) on Disposal Pre-tax loss Gain/(loss) on disposal of operations Class of Stock Class of Stock [Axis] Segment Reporting Reconciling Item For Operating Profit Loss From Segment To Consolidated [Line Items] Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items] Net deferred tax liabilities Deferred Tax Liabilities, Net Net deferred tax liabilities Net deferred tax liability Deferred tax liabilities Employee contributions Defined Benefit Plan, Plan Assets, Contributions by Plan Participant 4.500% senior notes due 2028 [Member] Senior Notes Due2028045 [Member] Senior notes due 2028, 045. Capitalized Contract Cost, Amortization Capitalized Contract Cost, Amortization Ireland [Member] IRELAND Current Income Tax Expense (Benefit), Total Total current tax expense Current Income Tax Expense (Benefit) Fair value of plan assets at end of year Defined Benefit Plan, Plan with Accumulated Benefit Obligation in Excess of Plan Assets, Plan Assets Capitalized Contract Cost [Abstract] Schedule of Amounts Recognized in Other Comprehensive Income (Loss) Schedule of Amounts Recognized in Other Comprehensive Income (Loss) [Table Text Block] Cybersecurity Risk Management, Strategy, and Governance [Line Items] Great Britain [Member] Great Britain [Member] Great Britain. Schedule of Projected Pension Contributions Schedule Of Projected Pension Contributions Table [Text Block] Schedule of projected pension contributions. Finance Leases [Abstract] Finance Lease, Liability, to be Paid, Fiscal Year Maturity [Abstract] Valuation And Qualifying Accounts Disclosure [Line Items] SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items] Nondesignated [Member] Not Designated as Hedging Instrument [Member] Not Designated as Hedging Instrument [Member] TOTAL LIABILITIES Liabilities Proceeds from Divestiture of Businesses, Net of Cash Divested, Total Proceeds from Divestiture of Businesses, Net of Cash Divested Cash proceeds from other disposal Internally-developed Software Asset [Member] Internally Developed Software Asset [Member] Internally-developed software asset. Financial Instruments [Domain] Restructuring and Related Cost, Incurred Cost Restructuring, Cost incurred Reclassification from AOCI, Current Period, before Tax, Attributable to Parent Gain/(loss) reclassified from Accumulated OCL into income (effective element) Debt Securities, Held-to-Maturity, Amortized Cost, after Allowance for Credit Loss, Maturity, Allocated and Single Maturity Date, Year One Due in one year or less carrying value Non-cash restructuring charges Restructuring Reserve, Settled without Cash Debt Securities, Held-to-Maturity, Fair Value, Maturity, Allocated and Single Maturity Date, Year One Due in one year or less fair value Employee Share Purchase Plan [Member] Employee share purchase plan. Employee Share Purchase Plan [Member] Tax differentials of non-U.S. jurisdictions Effective Income Tax Rate Reconciliation, Foreign Income Tax Rate Differential, Amount Derivative Liability, Statement of Financial Position [Extensible Enumeration] Expected return on plan assets Defined Benefit Plan, Expected Return (Loss) on Plan Assets Lessee, Operating Lease, Liability, to be Paid, Year Two Operating Lease, 2027 Defined Contribution Plan Tranche Two [Member] Defined Contribution Plan Tranche Two [Member] Defined contribution plan tranche two. Restricted Cash and Cash Equivalent Item [Line Items] Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Table] Disposal Groups, Including Discontinued Operations [Table] Deferred tax adjustment Income Tax Expense (Benefit), Continuing Operations, Adjustment of Deferred Tax (Asset) Liability Amortization of right-of-use assets Finance Lease, Right-of-Use Asset, Amortization Variable Rate Variable Rate [Axis] Dividends payable Dividends Payable, Current Balance at beginning of year Balance at end of year SEC Schedule, 12-09, Valuation Allowances and Reserves, Amount Finite-Lived Intangible Assets, Gross, Total Finite-lived intangible assets, gross carrying amount Finite-Lived Intangible Assets, Gross Diluted weighted-average number of shares outstanding (shares) Weighted Average Number of Shares Outstanding, Diluted Net adjustments on acquisition costs Net adjustments on acquisition costs Effective Income Tax Rate Reconciliation Net adjustments on Acquisition Costs Effective income tax rate reconciliation net adjustments on acquisition costs. Entity File Number Securities Act File Number Dividends paid Payments of Ordinary Dividends, Common Stock Percentage of lease denominated in U.S. dollars, Pounds Sterling or Euros Percentage Of Lease Denominated In Major Currencies Percentage of lease denominated in major currencies such as U.S. dollars, Pounds Sterling or Euros. Net assets/(liabilities) Defined Benefit Plan Fair Value Of Plan Assets Liabilities Net Value Defined benefit plan fair value of plan assets liabilities, net value. UNITED STATES [Member] Domestic Plan [Member] Schedule of Derivative Instruments Designated/Nondesignated As Hedging Instrument Effect on Condensed Consolidated Statements of Comprehensive Income Derivative Instruments, Gain (Loss) [Table Text Block] Cover [Abstract] Income from Continuing Operations before Income Taxes and Interest in Earnings of Associates [Line Items] Income From Continuing Operations Before Income Taxes And Interest In Earnings Of Associates [Line Items] Income from continuing operations before income taxes and interest in earnings of associates. Measurement Input Type Measurement Input Type [Axis] Lease Liability Payments Due Next Twelve Months Lease liability payments due next twelve months. Total Lease, 2026 Other employee-related liabilities Other Employee-related Liabilities, Current Total prepaid and other current assets Prepaid and other current assets Prepaid Expense and Other Assets, Current Forfeited (shares) Forfeited (shares) Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Forfeited in Period Taxes Payable, Current, Total Taxes Payable, Current Income taxes payable Accrued vacation Other Deferred Compensation Arrangements, Liability, Current Reclassification from AOCI, Current Period, Tax, Total Reclassification from AOCI, Current Period, Tax Reclassification from AOCI, Current Period, Tax Supplementary Information for Certain Balance Sheet Accounts Supplemental Balance Sheet Disclosures [Text Block] Discount rate - service cost Defined Benefit Plan Assumptions Used Calculating Net Periodic Benefit Cost Discount Rate Service Cost Defined benefit plan, assumptions used calculating net periodic benefit cost, discount rate, service cost. Property Lease Guarantee [Member] Property Lease Guarantee [Member] Summary of Valuation Allowance Summary of Valuation Allowance [Table Text Block] INCOME FROM OPERATIONS BEFORE INCOME TAXES AND INTEREST IN EARNINGS OF ASSOCIATES Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Noncontrolling Interest INCOME FROM OPERATIONS BEFORE INCOME TAXES AND INTEREST IN EARNINGS OF ASSOCIATES 2012 Equity Incentive Plan [Member] A2012 Equity Incentive Plan [Member] 2012 Equity Incentive Plan [Member] Carl Hess [Member] Carl Hess Carl Hess Revenue Benchmark [Member] Total Lease, Thereafter Lease Liability Payments Due After Year Five Amount of lessee's undiscounted obligation for lease payments for operating lease and finance lease, due after fifth fiscal year following latest fiscal year. Share-Based Compensation Arrangement by Share-Based Payment Award, Number of Shares Authorized Shares issued under ESPP Sale of Stock [Domain] Senior Notes Due204903875 [Member] 3.875% senior notes due 2049 [Member] Senior notes due 2049, 03875. Segment Information Segment Reporting Disclosure [Text Block] Fair value inputs, weighted-average discount rate Alternative Investment, Measurement Input Schedule of Benefit Obligations in Excess of Fair Value of Plan Assets Defined Benefit Plan, Plan with Projected Benefit Obligation in Excess of Plan Assets [Table Text Block] Derivative instruments [Member] AOCI, Derivative Qualifying as Hedge, Excluded Component, Parent [Member] Minority Interest [Line Items] Noncontrolling Interest [Line Items] Corporate, Non-Segment Segment Reporting, Reconciling Item, Corporate Nonsegment [Member] Liabilities for uncertain tax positions Unrecognized Tax Benefits Including Interest Amount of unrecognized tax benefits including interest. Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Vested, Number of Shares Shares vested under ESPP Valuation And Qualifying Accounts Disclosure [Table] SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Table] Subsequent Event [Table] Short-term Debt, Type Short-Term Debt, Type [Domain] Significant Accounting Policies And Recent Accounting Pronouncements [Table] Significant Accounting Policies And Recent Accounting Pronouncements [Table] Significant accounting policies and recent accounting pronouncements. Total Finite-lived intangible assets, net amount Finite-Lived Intangible Assets, Net, Ending Balance Finite-Lived Intangible Assets, Net, Beginning Balance Finite-Lived Intangible Assets, Net Share-based compensation and net settlements Adjustments To Additional Paid In Capital Sharebased Compensation And Net Settlements Adjustments to additional paid in capital, sharebased compensation and net settlements. Dec 31, 2022 [Member] December Thirty One Two Thousand and Twenty Two [Member] December thirty one two thousand and twenty two. Impact of change in rate on deferred tax balances Effective Income Tax Rate Reconciliation, Change in Enacted Tax Rate, Amount December 31 2021 Member. December 31 2021 [Member] December 31 2021 [Member] Deposits Assets, Current Certificate of deposit Charges incurred Restructuring Charges, Total Restructuring costs Restructuring costs Restructuring Charges Useful life Property, Plant and Equipment, Useful Life Short-term Debt, Type Short-Term Debt, Type [Axis] Recent Accounting Pronouncements New Accounting Pronouncements, Policy [Policy Text Block] Movement in Property, Plant and Equipment [Roll Forward] Movement in Property, Plant and Equipment [Roll Forward] Gain (Loss) on Disposition of Assets, Total Gain (Loss) on Disposition of Assets Gain on disposal Gain of disposal price and other adjustments Claims, lawsuits and other proceedings Estimated Litigation Liability, Noncurrent Comprehensive Income (Loss) Comprehensive Income (Loss) [Table Text Block] Ownership Ownership [Axis] Summary of Cash Paid for Income Taxes, Net of Refunds by Jurisdiction [Table Text Block] Tabular disclosure of cash paid for income taxes, net of refunds by jurisdiction . Summary of Cash Paid for Income Taxes, Net of Refunds Vesting period Share-Based Compensation Arrangement by Share-Based Payment Award, Award Vesting Period Accumulated Other Comprehensive Loss Comprehensive Income (Loss) Note [Text Block] Final total consideration received from sale of subsidiary Total upfront cash consideration received from sale of subsidiary Total consideration received from sale of subsidiary Depreciation, Total Depreciation expense Depreciation Depreciation Capital contribution obligation Capital Contribution Obligation Capital contribution obligation. Carrying Value [Member] Reported Value Measurement [Member] Health care cost trend - Ultimate rate Defined Benefit Plan, Ultimate Health Care Cost Trend Rate Proceeds from Issuance of Long-term Debt, Total Proceeds from long-term debt issuance Proceeds from Issuance of Long-Term Debt Employee Services Share Based Compensation, Tax Benefit Realized From Vesting Of RSUs Employee Services Share Based Compensation Tax Benefit Realized From Vesting Of R S Us Employee Services Share Based Compensation, Tax Benefit Realized From Vesting Of RSUs Corporate [Member] Corporate Segment [Member] Other Comprehensive (Income) Loss, Defined Benefit Plan, after Reclassification Adjustment, after Tax, Total Defined pension and post-retirement benefits Other Comprehensive (Income) Loss, Defined Benefit Plan, after Reclassification Adjustment, after Tax Real estate lease term Lessee, Operating Lease, Term of Contract Common Stock, Shares, Outstanding, Ending Balance Common Stock, Shares, Outstanding, Beginning Balance Ordinary shares, shares outstanding Common Stock, Shares, Outstanding Operating Lease, Current lease liabilities Current lease liabilities Operating Lease, Liability, Current Fiduciary funds (included in fiduciary assets) Other Restricted Assets, Current Revenue, Remaining Performance Obligation Revenue, Remaining Performance Obligation, Amount Amortization of unrecognized prior service (credit)/cost Defined Benefit Plan, Amortization of Prior Service Cost (Credit) Cybersecurity Risk Management Processes Integrated [Flag] Document Transition Report Document Transition Report Share Based Compensation Arrangement by Share Based Payment Award, Equity Instruments Other than Options, Purchased in Period, Fair Value Share based compensation arrangement by share based payment award, equity instruments other than options, purchased in period, fair value Fair value of stock purchased Business Combination, Contingent Consideration [Table] Deferred Tax Assets, Net Net deferred tax assets Net deferred tax asset Operating Expenses Total segment expenses Debt Securities, Held-to-Maturity, Fair Value Aggregate fair value Impairment Asset Impairment Charges, Total Asset Impairment Charges Impairment Portion of pension and OPEB obligation attributed to disclosed plans (as a percent) Defined Benefit Plans Percentage Of Obligation From Plans Defined benefit plans, percentage of obligation from plans. Repurchase of shares Payments for Repurchase of Common Stock Net Periodic Defined Benefits Expense (Reversal of Expense), Excluding Service Cost Component Net periodic pension and postretirement benefit (cost)/credit Schedule of Components of Income Tax Expense (Benefit) [Table Text Block] Provision for Benefit From Income Taxes Comprehensive Income (Loss), Net of Tax, Including Portion Attributable to Noncontrolling Interest Comprehensive income/(loss) before non-controlling interests Comprehensive income/(loss) before non-controlling interests Liability, Defined Benefit Plan, Noncurrent, Total Non-current liability for pension benefits Liability for pension benefits Liability, Defined Benefit Plan, Noncurrent Statement of Cash Flows [Abstract] Value of receivables in initial transfer Value of Receivables in Initial Transfer Value of receivables in initial transfer. Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract] Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract] Cost, Amortization Amortization U.S. federal taxes Current Federal Tax Expense (Benefit) Assets: Assets, Fair Value Disclosure [Abstract] Operating Activities [Domain] Business Combination, Contingent Consideration, Range of Outcomes, Maximum, Amount Employee contributions to ESPP Employee Stock Ownership Plan (ESOP), Cash Contributions to ESOP Derivative Asset, Statement of Financial Position [Extensible Enumeration] Payments to Acquire Businesses, Net of Cash Acquired, Total Acquisitions of operations, net of cash acquired Payments to Acquire Businesses, Net of Cash Acquired Contingent and deferred consideration on acquisitions Business Combination Contingent Consideration Liability And Deferred Consideration Noncurrent Business combination, contingent consideration, liability and deferred consideration, noncurrent. Finite Lived Intangible Assets [Line Items] Finite-Lived Intangible Assets [Line Items] Earnings Per Share Earnings Per Share [Text Block] Performance Targets [Member] Performance targets. Performance Targets Reduction in liability for unrecognized tax benefits Unrecognized Tax Benefits that Would Impact Effective Tax Rate Debt Security, Government, Non-US [Member] Government bonds [Member] Discontinued Operations and Disposal Groups [Abstract] Schedule of Share-based Compensation, Restricted Stock Units Award Activity Share-Based Payment Arrangement, Restricted Stock Unit, Activity [Table Text Block] Non-cash consideration received Other Significant Noncash Transaction, Value of Consideration Received Cybersecurity Risk Management Processes Integrated [Text Block] NET INCOME/(LOSS) ATTRIBUTABLE TO WTW Net income/(loss) attributable to WTW Pensions Pension and Other Postretirement Plans, Pensions, Policy [Policy Text Block] Total Lease, Total lease liabilities Lease Liability Present value of lessee's discounted obligation for lease payments from both operating lease and finance lease. Lease Liability Payments Due Year Three Amount of lessee's undiscounted obligation for lease payments for operating lease and finance lease, due in third fiscal year following latest fiscal year. Total Lease, 2028 2.950% senior notes due 2029 [Member] Senior Notes Due202902950 [Member] Senior notes due 2029, 02950. Operating lease cost Operating Lease, Cost Income Tax Contingency [Line Items] Income Tax Contingency [Line Items] Operating lease liabilities Deferred Tax Assets, Tax Deferred Expense, Reserves and Accruals, Deferred Rent Corporate income and other taxes Income Taxes Receivable, Current Intangible Assets, Net (Excluding Goodwill), Total Other intangible assets, net Intangible Assets, Net (Excluding Goodwill) Reimbursed Expenses [Member] Reimbursed Expenses [Member] Reimbursed Expenses [Member] Other taxes payable Accrual for Taxes Other than Income Taxes, Current Operating leases Operating Lease, Payments ASSETS Assets [Abstract] Income Tax Authority, Name Income Tax Authority, Name [Axis] Due in greater than five years fair value Held to Maturity Securities Debt Maturities After Five Years Fair Value Held to maturity securities debt maturities after five years fair value. Risk-free interest rate Share-Based Compensation Arrangement by Share-Based Payment Award, Fair Value Assumptions, Risk Free Interest Rate Repayment of debt Repayments of Debt Fiduciary assets transferred Business Combination Fiduciary Assets Transferred Business combination fiduciary assets transferred. Restructuring and Related Activities [Abstract] Transition Services Agreement [Member] Transition Services Agreement. Revenue from Rights Concentration Risk [Member] Document Fiscal Year Focus Document Fiscal Year Focus Land and Building [Member] Land and Building [Member] Other Miscellaneous Other Non Operating Income Expense Miscellaneous other non-operating income expense. Abandonment of long-lived asset Abandonment Abandonment Of Long Lived Asset Abandonment of long-lived asset. Schedule of Accumulated Other Comprehensive Income (Loss) Schedule of Accumulated Other Comprehensive Income (Loss) [Table Text Block] Concentration Risk Benchmark [Domain] Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Period Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Period Cash Provided by (Used in) Investing Activity, Including Discontinued Operation [Abstract] CASH FLOWS FROM/(USED IN) INVESTING ACTIVITIES Retirement Benefits [Abstract] IRR [Member] Investment Risk And Reinsurance [Member] Investment, risk and reinsurance. Decreases related to lapse in statute of limitations Unrecognized Tax Benefits, Reduction Resulting from Lapse of Applicable Statute of Limitations Schedule of Income before Income Tax, Domestic and Foreign [Table Text Block] Income From Operations Before Income Taxes and Interest in Earnings of Associates by Taxing Jurisdiction Goodwill, Impairment Loss, Statement of Income or Comprehensive Income [Extensible Enumeration] Schedule of Net Periodic Benefit Cost Schedule of Net Benefit Costs [Table Text Block] Employer matching contribution, percent of match Defined Contribution Plan, Employer Matching Contribution, Percent of Match Employee contributions Defined Benefit Plan, Benefit Obligation, Contributions by Plan Participant Schedule of Weighted Average Term and Discount Rates Schedule Of Weighted Average Term And Discount Rates For Operating And Finance Lease Table [Text Block] Schedule of weighted average term and discount rates for operating and finance lease. Obligations assumed Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Purchases Cumulative translation adjustment and other adjustments Unrecognized Tax Benefits Other Increase Decrease Unrecognized Tax Benefits, Other Increase (Decrease). Preliminary pre-tax gain on sale Gain on disposal Net change in primarily related to the sale of business Net (gain)/loss on disposal of operations Income Tax Reconciliation Earnout Received and Changes in Uncertain Tax Positions Income tax reconciliation earnout received and changes in uncertain tax positions. Earnout received and changes in uncertain tax positions U.S. federal taxes Deferred Federal Income Tax Expense (Benefit) Shares Issued, Value, Share-based Payment Arrangement, after Forfeiture, Total Issuance of shares under employee stock compensation plans Shares Issued, Value, Share-Based Payment Arrangement, after Forfeiture Restructuring Cost and Reserve [Line Items] Finite-Lived Intangible Asset, Expected Amortization, Year One 2026 Deferred tax assets: Components of Deferred Tax Assets [Abstract] Disposals Property, Plant and Equipment, Disposals Costs To Obtain [Member] Costs To Obtain Costs To Obtain [Member] Settlements Defined Benefit Plan, Plan Assets, Payment for Settlement Defined Benefit Plan Purchase of Annuity Contract Vested, Average Intrinsic Value (in dollars per share) Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Vested in Period, Intrinsic Value, Amount Per Share Private equity [Member] Private Equity Funds [Member] Total Long-term lease liabilities Lease Liability Noncurrent Lease liability non current. Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward] Unrecognized Tax Benefits [Roll Forward] 2.125% senior notes due 2022 [Member] Senior Notes Due202202125 [Member] Senior notes due 2022, 02125. Rate of increase in compensation levels Defined Benefit Plan, Assumptions Used Calculating Benefit Obligation, Rate of Compensation Increase Schedule of Accumulated Benefit Obligations in Excess of Fair Value of Plan Assets Defined Benefit Plan, Plan with Accumulated Benefit Obligation in Excess of Plan Assets [Table Text Block] Cash received from exercise of stock options Proceeds from Stock Options Exercised Fair Value Disclosures [Abstract] Transaction and Transformation, Net [Policy Text Block] Transaction and Transformation, Net. Transaction and Transformation Commitments and Contingencies Disclosure [Abstract] Canada [Member] Canada - Federal [Member] CANADA Employee Status Employee Status [Axis] Employee status. Capital Expenditures. Capital Expenditures [Member] Derivatives [Member] Derivative [Member] Deferred consideration Deferred Consideration Liabilities Deferred consideration liabilities. North America [Member] North America [Member] Effective Income Tax Rate Reconciliation, Tax Credit, Amount Effective Income Tax Rate Reconciliation, Tax Credit, Amount, Total Foreign tax credits Foreign tax credits Lessee, Operating Lease, Liability, to be Paid, Year One Operating Lease, 2026 Operating Leases, Rent Expense, Total Rent expense, net of sublease income Operating Leases, Rent Expense Effective Income Tax Rate Reconciliation [Line Items] Federal Funds Effective Rate. Federal Funds Effective Rate [Member] Federal Funds Effective Rate [Member] Supplemental Disclosures of Cash Flow Information Cash Flow, Supplemental Disclosures [Text Block] Contract with Customer, Asset, after Allowance for Credit Loss, Current, Total Contract with Customer, Asset, after Allowance for Credit Loss, Current Contract asset, Current Payment for Contingent Consideration Liability, Financing Activities Payments of deferred and contingent consideration related to acquisitions Debt Instrument Debt Instrument [Axis] Derivative Instrument Derivative Instrument [Axis] Operating Lease, Thereafter Lessee, Operating Lease, Liability, to be Paid, after Year Five Interest cost Defined Benefit Plan, Interest Cost Share-Based Payment Arrangement [Abstract] Capitalized Contract Cost [Line Items] Share-Based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Amount Compensation cost not yet recognized Share-based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Amount, Total Cost of intangible assets, net of related amortization Deferred Tax Liabilities, Intangible Assets Cost of intangible assets, net of related amortization Sale of Stock [Axis] Derivatives Derivatives, Policy [Policy Text Block] Concentration Risk, Percentage Concentration risk percentage Defined Benefit Plan, Expected Future Benefit Payment, Year One 2026 Expected future benefit payments, total Defined Benefit Plan Expected Future Benefit Payments Defined benefit plan expected future benefit payments. Total revenue Revenue Revenues Total segment revenue Cash Provided by (Used in) Investing Activity, Including Discontinued Operation Net cash from/(used in) investing activities Additions Property, Plant and Equipment, Additions Schedule of net plan investments reconciliation to total fair value of plan assets. Schedule of Net Plan Investments Reconciliation To Total Fair Value Of Plan Assets Schedule Of Net Plan Investments Reconciliation To Total Fair Value Of Plan Assets Table [Text Block] Finance Leases, Weighted-average remaining term (in years) Finance Lease, Weighted Average Remaining Lease Term Senior Notes Due205405900 [Member] Senior notes due 2054, 05900. 5.900% senior notes due 2054 [Member] Title of 12(b) Security Title of 12(b) Security Schedule Of Segment Reporting Information By Segment [Table] Schedule of Segment Reporting Information, by Segment [Table] Employee-related Liabilities, Total Liability recognized Employee-related Liabilities Federal Funds Effective Swap Rate [Member] Fed Funds Effective Rate Overnight Index Swap Rate [Member] Derivative Financial Instruments Derivative Instruments and Hedging Activities Disclosure [Text Block] Income Tax Paid, by Individual Jurisdiction [Table] Forfeited, Weighted Average Grant Date Fair Value (in dollars per share) Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Forfeitures, Weighted Average Grant Date Fair Value Related and Nonrelated Parties [Domain] Thereafter Long-Term Debt, Maturity, after Year Five Income Taxes Income Tax Disclosure [Text Block] Total Right-of-use assets Lease Right Of Use Asset Amount of lessee's right to use underlying asset under both operating lease and finance lease. LIBOR [Member] Libor. Total other non-current liabilities Other non-current liabilities Other Liabilities, Noncurrent Business Combination, Achieved in Stages, Preacquisition Equity Interest in Acquiree, Remeasurement, Gain Gain on disposal of operations Restructuring Plan [Domain] Net book value Finance Lease, Right-of-use assets Finance Lease, Right-of-Use Asset, after Accumulated Amortization Legal Entity [Axis] Legal Entity Changes in operating assets and liabilities, net of effects from purchase of subsidiaries: Adjustment to Reconcile Net Income to Cash Provided by (Used in) Operating Activity, Increase (Decrease) in Operating Capital [Abstract] Property, Plant and Equipment Property, Plant and Equipment [Table Text Block] Defined Benefit Plan, Plan Assets, Amount, Total Fair value of plan assets Fair value of plan assets, beginning of year Fair value of plan assets, end of year Defined Benefit Plan, Plan Assets, Amount Debt Securities, Held-to-Maturity, Fair Value, Maturity, Allocated and Single Maturity Date, after Year One Through Five Due in one year through five years fair value Income Tax Disclosure [Abstract] Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Table] Fair Value, Recurring and Nonrecurring [Table] Accumulated depreciation Property, Plant, and Equipment and Finance Lease Right-of-Use Asset, Accumulated Depreciation and Amortization Interest income Interest Income Interest Income. Unrecognized tax benefits Balance at beginning of year Balance at end of year Unrecognized Tax Benefits Defined benefit plan plan assets and addition disposal. Defined Benefit Plan Plan Assets And Addition Disposal Plan (disposal)/addition Collateralized Facility [Member] Collateralized Facility [Member] Collateralized facility. Projected Annual Cost Savings by End of 2024 [Member] Projected annual cost savings by end of 2024. Debt Instrument Commitment Fee Percentage Debt Instrument Commitment Fee Percentage Debt instrument commitment fee percentage. Dispositions. Dispositions [Abstract] UNITED KINGDOM [Member] United Kingdom [Member] UNITED KINGDOM Measurement Frequency Measurement Frequency [Domain] Income Statement Location Statement of Income Location, Balance [Axis] Senior Notes [Member] Senior Notes [Member] Trading Symbol Trading Symbol Schedule Of Finite Lived Intangible Assets [Table] Intangible Asset, Finite-Lived [Table] Fixed Assets Property, Plant and Equipment Disclosure [Text Block] Defined benefit plan required employee contribution rate Defined Benefit Plan Required Employee Contribution Rate Defined benefit plan required employee contribution rate. Capitalized Contract Cost, Additions Capitalized Contract Cost Additions Capitalized Contract Cost, Additions Transaction and transformation Transaction and integration expense Business Combination Integration Related Costs Credits Business combination integration related costs credits. Subsequent Event Type [Axis] Fees earned under service agreement Fees earned under service agreement. Defined Contribution Plan Tranches Defined Contribution Plan Tranches [Axis] Defined contribution plan tranches. Changes in the Net Carrying Amount of the Components of Finite-Lived Intangible Assets Schedule of Finite-Lived Intangible Assets [Table Text Block] CASH FLOWS USED IN FINANCING ACTIVITIES Cash Provided by (Used in) Financing Activity, Including Discontinued Operation [Abstract] Commitment fee percentage Line of Credit Facility, Unused Capacity, Commitment Fee Percentage Expected life (years) Share-Based Compensation Arrangement by Share-Based Payment Award, Fair Value Assumptions, Expected Term Recurring [Member] Fair Value, Recurring [Member] Disposals Accumulated Depreciation, Depletion and Amortization, Sale or Disposal of Property, Plant and Equipment Finite-Lived Intangible Assets, Amortization Expense, Maturity Schedule [Abstract] Finite-Lived Intangible Assets, Amortization Expense, Maturity Schedule [Abstract] Operating leases Operating Lease, Total future lease payments Lessee, Operating Lease, Liability, to be Paid Operating Lease, Interest Lessee, Operating Lease, Liability, Undiscounted Excess Amount Other [Member] Other Restructuring [Member] Interest and Debt Expense, Total Repayment of Interest and debt expense Interest and Debt Expense Equity Components Equity Components [Axis] Financial derivative transactions Deferred Tax Assets, Derivative Instruments Change in Benefit Obligation Defined Benefit Plan, Change in Benefit Obligation [Roll Forward] Percentage of entity voting rights Percentage Of Voting Rights Percentage of voting rights. Debt Securities, Held-to-Maturity [Table Text Block] Summarizes the Types of Holdings and Related Values Equity Component Equity Component [Domain] Asset Class [Axis] 1-year Term Loan Facility Matures 2016 [Member] One Year Term Loan Facility Due2016 [Member] One year term loan facility due 2016. Accrued discretionary and incentive compensation Accrued Discretionary And Incentive Compensation Carrying value as of the balance sheet date of obligations incurred and payable for incentive compensation awarded to employees and directors or earned by them based on the terms of one or more relevant arrangements. Defined Benefit Plan, Benefit Obligation, (Increase) Decrease for Settlement, Total Settlements Defined Benefit Plan, Benefit Obligation, (Increase) Decrease for Settlement Settlements Goodwill and Intangible Assets Disclosure [Abstract] Held to Maturity Securities Debt Maturities After Five Years Net Carrying Amount Held to maturity securities debt maturities after five years net carrying amount. Due in greater than five years carrying value Valuation Allowance of Deferred Tax Assets [Member] SEC Schedule, 12-09, Valuation Allowance, Deferred Tax Asset [Member] Document Annual Report Document Annual Report Business Acquisition Business Combination [Axis] Contingent consideration Obligations, Fair Value Disclosure Rate of increase in compensation levels Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Rate of Compensation Increase Provisions Increase Decrease In Provision For Liabilities Increase decrease in provision for liabilities. SOFR Adjustment [Member] Secured Overnight Financing Rate (SOFR) Overnight Index Swap Rate Adjustment [Member] Secured overnight financing rate (SOFR) overnight index swap rate adjustment. Revenue Remaining Performance Obligation Expected Timing Of Satisfaction [Table] Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Table] Effective Income Tax Rate Reconciliation, Tax Contingency, Amount Effective Income Tax Rate Reconciliation, Tax Contingency, Amount, Total Changes in uncertain tax positions Changes in uncertain tax positions Total Current lease liabilities Lease Liability Current Lease liability current. Above Target Performance [Member] Above target performance. Above Target Performance Deferred income tax expense benefit including discontinued operations. Deferred Income Tax Expense Benefit Including Discontinued Operations Provision for/(benefit from) deferred income taxes AOCI Attributable to Noncontrolling Interest [Member] AOCI Attributable to Noncontrolling Interest [Member] Health care cost trend - Initial rate Defined Benefit Plan, Health Care Cost Trend Rate Assumed, Next Fiscal Year Maximum [Member] Maximum [Member] Maximum [Member] Lease Liability Payments Due Year Four Amount of lessee's undiscounted obligation for lease payments for finance lease, due in fourth fiscal year following latest fiscal year. Total Lease, 2029 Defined Benefit Plan, Roll Forwards [Abstract] Designated [Member] Designated as Hedging Instrument [Member] Designated as Hedging Instrument [Member] Total provision for liabilities Provision for liabilities Provision For Liabilities Non Current Provision for liabilities non current. Statistical Measurement Statistical Measurement [Axis] Exercised, Weighted Average Exercise Price Exercised, Weighted Average Exercise Price (in dollars per share) Share-Based Compensation Arrangements by Share-Based Payment Award, Options, Exercises in Period, Weighted Average Exercise Price Finite-lived intangible assets, accumulated amortization Finite-Lived Intangible Assets, Accumulated Amortization Accrued retirement benefits Deferred Tax Assets, Tax Deferred Expense, Compensation and Benefits, Postretirement Benefits Defined Benefit Plan, Plan Assets, Foreign Currency Translation Gain (Loss) Foreign currency changes Foreign exchange Foreign currency adjustment ESPP [Member] ESPP. ESPP [Member] Other comprehensive income/(loss), net of tax, before non-controlling interests Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Noncontrolling Interest Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Noncontrolling Interest, Total Other comprehensive income/(loss), net of tax, before non-controlling interests Finance leases Finance Lease, Principal Payments Line of credit maturity date Line of Credit Facility, Expiration Date Insurance recovery receivables Insurance Settlements Receivable, Noncurrent Term Loan Due 2019 [Member] Term Loan Due December2019 [Member] Term Loan Due December 2019 [Member] Principles of Consolidation Consolidation, Policy [Policy Text Block] Goodwill [Roll Forward] Goodwill [Roll Forward] Total equity Equity, beginning balance Equity, ending balance Equity, Including Portion Attributable to Noncontrolling Interest Share based compensation arrangement by share based payment award equity instruments other than options vested in prior period. Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Vested In Prior Period RSU vested in prior year Income Tax Contingency [Table] Income Tax Contingency [Table] Capitalized Contract Cost [Axis] Prepaid retirement benefits Deferred Tax Liabilities, Prepaid Expenses Prepaid retirement benefits Deferred Tax Assets, Operating Loss Carryforwards, Total Net operating losses Deferred Tax Assets, Operating Loss Carryforwards Value of obligation in initial transfer Value of Obligation in Initial Transfer Value of obligation in initial transfer. Cybersecurity Risk Management Processes for Assessing, Identifying, and Managing Threats [Text Block] TRANZACT [Member] TRANZACT. TRANZACT [Member] Base Erosion Anti-Abuse Tax (BEAT) Base Erosion Anti-Abuse Tax (BEAT) Effective Income Tax Rate Reconciliation, BEAT, Amount Current Income Tax Expense (Benefit) for Ireland Current income tax expense (benefit) for ireland. Ireland Ireland Purchases Defined Benefit Plan, Plan Assets Level 3 Reconciliation, Increase for Purchase Effective Income Tax Rate Reconciliation, State and Local Income Taxes, Percent Impact of U.S. state and local taxes (net of federal taxes), Percentage Depreciation expense Depreciation Expense Excluding Abandonment Of Internally Developed Software Asset Depreciation expense excluding abandonment of an internally-developed software asset. Schedule of Future Estimated Amortization Expense for Amortizable Intangible Assets Schedule of Finite-Lived Intangible Assets, Future Amortization Expense [Table Text Block] Entity Public Float Entity Public Float Offering period discount Share-Based Compensation Arrangement by Share-Based Payment Award, Discount from Market Price, Offering Date Share-Based Compensation Arrangement by Share-Based Payment Award, Fair Value Assumptions, Expected Volatility Rate Expected volatility Preference shares, shares authorized Preferred Stock, Shares Authorized Fiduciary [Member] Fiduciary [Member] Fiduciary. Total deferred revenue and accrued expenses Deferred revenue and accrued expenses Deferred Revenue And Accrued Liabilities Current Deferred revenue and accrued liabilities current. Interest payable Interest Payable, Current Other Comprehensive Income Loss Cash Flow Hedge Gain Loss Before Reclassification Before Tax Other comprehensive income loss cash flow hedge gain loss before reclassification before tax Gain/(loss) recognized in OCL (effective element) Comprehensive Income (Loss), Net of Tax, Attributable to Noncontrolling Interest, Total Comprehensive income attributable to non-controlling interests Comprehensive Income (Loss), Net of Tax, Attributable to Noncontrolling Interest Total costs of providing services Total costs of providing services Costs and Expenses Finite-Lived Intangible Assets by Major Class Finite-Lived Intangible Assets by Major Class [Axis] Acquisitions and Divestitures Mergers, Acquisitions and Dispositions Disclosures [Text Block] Schedule of Current and Long-term Debt Schedule of Debt [Table Text Block] Cash paid for employee taxes on withholding shares Payment, Tax Withholding, Share-Based Payment Arrangement Fair value of plan liabilities Defined Benefit Plan Fair Value Of Plan Assets Liabilities Defined Benefit plan, fair value of plan assets, liabilities. Fiduciary Cash [Member] Fiduciary Cash [Member] Fiduciary cash Member France [Member] FRANCE Revolving $800 million Credit Facility [Member] Revolving800 Million Dollar Credit Facility [Member] Revolving 800 million dollar credit facility. Equity based payment. Equity Based Payment [Member] Equity Based Payment [Member] Effective Income Tax Rate Reconciliation, Cross-Border Tax Effect, Percent Effective Income Tax Rate Reconciliation, Cross-Border Tax Effect, Percent, Total Effect of cross-border tax laws, Percentage Effect of cross-border tax laws, Percentage Significant Change in Unrecognized Tax Benefits is Reasonably Possible, Nature of Uncertainty Significant Change in Unrecognized Tax Benefits is Reasonably Possible, Nature of Uncertainty [Domain] Revenue Revenue from Contract with Customer [Text Block] Business Combination [Table] Entity Registrant Name Entity Registrant Name Debt Debt Disclosure [Text Block] Accumulated benefit obligation at end of year Defined Benefit Plan, Plan with Accumulated Benefit Obligation in Excess of Plan Assets, Accumulated Benefit Obligation Entity Voluntary Filers Entity Voluntary Filers Finite-Lived Intangible Asset, Expected Amortization, Year Two 2027 Third Amended and Restated Revolving Credit Facility [Member] Third amended and restated revolving credit facility. Third Amended and Restated Revolving Credit Facility [Member] Other income, net Other Nonoperating Income (Expense) Other (loss)/income, net Other (loss)/income, net Accumulated Other Comprehensive Income Loss [Table] Accumulated Other Comprehensive Income (Loss) [Table] U.S. state and local taxes Deferred State and Local Income Tax Expense (Benefit) Costs To Fulfill [Member] Costs To Fulfill [Member] Costs To Fulfill Balance Sheet Date Balance Sheet Date [Axis] Balance sheet date. Other comprehensive (loss)/income Other Comprehensive Income Loss Net Of Tax Including Portion Attributable To Nonredeemable Noncontrolling Interest Other comprehensive income (loss), net of tax including portion attributable to nonredeemable noncontrolling interest. Subsequent Events [Abstract] Annual cost savings of program Effect on Future Earnings, Amount Cybersecurity Risk Management Positions or Committees Responsible [Flag] Schedule of Other Nonoperating Income (Expense) [Table Text Block] Schedule of Other Nonoperating (Loss)/Income SOFR [Member] Secured Overnight Financing Rate (SOFR) Overnight Index Swap Rate [Member] Finite-Lived Intangible Asset, Expected Amortization, Year Three 2028 Income Tax Expense (Benefit), Total Total provision for income taxes Income Tax Expense (Benefit) Provision for income taxes Income tax expense (benefit) 7.000% senior notes due 2019 [Member] Senior Notes Due20190700 [Member] Senior notes due 2019, 0700. Pension plan asset target allocations Defined Benefit Plan, Plan Assets, Target Allocation, Percentage Measurement Frequency Measurement Frequency [Axis] Other Investments, Total Other investments Other Investments Defined benefit plan employees covered percentage Defined Benefit Plan Employees Covered Percentage Defined benefit plan employees covered percentage. December Thirty One Two Thousand And Twenty Four [Member] December thirty one two thousand and twenty four. Dec 31, 2024 [Member] Payments to Acquire Productive Assets Payments to Acquire Productive Assets, Total Additions to fixed assets and software Defined Benefit Plan, Expected Future Benefit Payment, Year Five 2030 Insurance contracts [Member] Insurance Contract, Rights and Obligations [Member] Defined Benefit Plan, Plan Assets Level 3 Reconciliation, Increase (Decrease) for Actual Return (Loss) on Plan Assets Still Held Unrealized loss Business Combination, Contingent Consideration, Type [Axis] Costs of providing services Costs and Expenses [Abstract] Share-based Compensation Arrangement by Share-based Payment Award [Line Items] Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items] Fair value level three transfers amount. Fair Value Level Three Transfers Amount Fair value significant transfers to or from Level 3 Entity Common Stock, Shares Outstanding Entity Common Stock, Shares Outstanding Compensation Related Costs, Policy [Policy Text Block] Employee Share Purchase Plan Liability Class Liability Class [Axis] Qualified Plan [Member] Qualified Plan [Member] Other Income and Other Expense Disclosure [Text Block] Other (Loss)/Income, Net Amortization of unrecognized prior service credit/(cost) Other Comprehensive (Income) Loss, Defined Benefit Plan, Prior Service Cost (Credit), Reclassification Adjustment from AOCI, before Tax Foreign Countries Member Total Foreign Countries [Member] Foreign Countries [Member] Accumulated Other Comprehensive Income (Loss), Net of Tax, Total Accumulated other comprehensive loss, net of tax Accumulated Other Comprehensive Income (Loss), Net of Tax Consolidation Items Consolidation Items [Axis] Pending Acquisitions [Member] Pending acquisitions. Pending Acquisitions Commitments and Contingencies, Policy [Policy Text Block] Commitments, Contingencies and Provisions for Liabilities Cash payments Cash payments Payments for Restructuring Granted units Granted (shares) Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Grants in Period Assumed debt related to borrowings Secured Long-Term Debt, Noncurrent TOTAL ASSETS Assets Schedule Of Property Plant And Equipment [Table] Property, Plant and Equipment [Table] (Purchase)/sale of investments Payments for (Proceeds from) Investments Payments for (Proceeds from) Investments, Total Sale/(purchase) of investments Transaction and Integration Expense [Member] Transaction Integration Expense [Member] Transaction integration expense. Revolving 1.5 Billion Dollar Credit Facility [Member] Revolving15 Billion Dollar Credit Facility [Member] Revolving 15 Billion Dollar Credit Facility. Income Statement [Abstract] Restructuring Cost [Table] Finance leases Finance Lease, Interest Payment on Liability Fair Value of Financial Instruments Fair Value of Financial Instruments, Policy [Policy Text Block] Senior Notes [Member] Interest on Senior Notes [Member] Interest On Senior Notes [Member] Interest on senior notes. Decreases related to tax positions in prior years Unrecognized Tax Benefits, Decrease Resulting from Prior Period Tax Positions Share-Based Compensation Share-Based Payment Arrangement [Policy Text Block] Amortization of unrecognized actuarial loss Defined Benefit Plan, Amortization of Gain (Loss) Description of interest accrual date Debt Instrument Interest Accrual Date Description Debt instrument interest accrual date description. Deferred Income Tax Expense (Benefit), Total Deferred income tax benefit Deferred Income Tax Expense (Benefit) (Benefit from)/provision for deferred income taxes Total deferred tax (expense)/benefit Technology Modernization [Member] Technology modernization [Member] Technology modernization. Senior Notes Due 2021 and 2026 [Member] Senior Notes Due2021and2026 [Member] Senior Notes Due 2021 and 2026 [Member] Consulting Business [Member] Consulting business. Consulting Business [Member] Al-Futtaim Willis [Member] Al-futtaim willis member. Al-Futtaim Willis Finance lease cost: Lease, Cost [Abstract] Share based compensation Arrangement by Share based Payment Award, Fair Value Assumptions, Average Correlation Coefficient of Peers Share based compensation arrangement by share based payment award, fair value assumptions, average correlation coefficient of peers. Average correlation coefficient of peer companies Vested (shares) Vested (shares) Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Vested in Period Number of shares vested Schedule of Allocation of Plan Assets Schedule of Allocation of Plan Assets [Table Text Block] Business Combination [Abstract] Accounts Payable, Other, Current Accounts payable, accrued liabilities and deferred revenue — Diluted: income from continuing operations Earnings Per Share, Diluted Diluted earnings/(loss) per share Lease Liability Payments Due Year Five Amount of lessee's undiscounted obligation for lease payments for operating lease and finance lease, due in fifth fiscal year following latest fiscal year. Total Lease, 2030 Schedule of Segment Reporting Information, by Segment Schedule of Segment Reporting Information, by Segment [Table Text Block] Operating Segments [Member] Operating Segments [Member] Term Loan Facility [Member] Term Loan Facility [Member] Term loan facility. Finite-Lived Intangible Asset, Expected Amortization, Year Five 2030 Dividends, Common Stock, Total Dividends declared Dividends, Common Stock Retirement Plan Tax Status Retirement Plan Tax Status [Axis] City Area Code City Area Code December312021 [Member] December 31 2021 [Member] December 31,2021. Tranzact Collateralized Facility [Member] Tranzact Collateralized Facility [Member] Tranzact collateralized facility. Components on the Consolidated Balance Sheet Defined Benefit Plan, Amounts for Asset (Liability) Recognized in Statement of Financial Position Other comprehensive income/(loss), total Other Comprehensive Income (Loss), Net of Tax Other comprehensive income/(loss), net of tax, before non-controlling interests Auditor Name Finance leases Finance Lease, Long-term lease liabilities Finance Lease, Liability, Noncurrent Accumulated other comprehensive loss Defined Benefit Plan, Accumulated Other Comprehensive (Income) Loss, before Tax Up Front [Member] Up front. Up-Front Summary of Retrospectively-adjusted Quarterly Financial Data Quarterly Financial Information [Table Text Block] Finite-lived Intangible Assets [Roll Forward] Finite-Lived Intangible Assets [Roll Forward] Debt instrument, face amount Debt Instrument, Face Amount Cash outflow of cash and fiduciary cash related to settlement. Cash outflow of cash and non-fiduciary cash related to settlement. Cash Divested from Deconsolidation Cash and fiduciary funds transferred in sale of operations Maximum borrowing capacity Line of Credit Facility, Maximum Borrowing Capacity Business Combination [Line Items] Vesting period Defined Contribution Plan Employers Matching Contribution Employee Vesting Period Defined contribution plan employers matching contribution employee vesting period. International [Member] International [Member] International. Schedule Of Defined Benefit Plans Disclosures [Table] Defined Benefit Plan [Table] Other [Member] Other Intangible Assets [Member] Open Tax Years Open Tax Years Open tax years. Variable Lease, Cost Variable lease cost Health care cost trend - ultimate rate year Defined Benefit Plan, Year Health Care Cost Trend Rate Reaches Ultimate Trend Rate Proceeds from Income Tax Refund, Federal U.S. federal capital loss carryback refund claim Schedule of Acquired Intangible Assets Amortized Schedule Of Finite Lived Intangible Assets Amortization Basis And Expected Life Table [Text Block] Schedule​ of finite​ lived ​intangible​ assets​ amortization basis and expected life. Transformation Program [Member] Transformation Program [Member] Transformation program. Operating Leases, Weighted-average remaining term (in years) Operating Lease, Weighted Average Remaining Lease Term Fair Value, Liability, Recurring Basis, Unobservable Input Reconciliation, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration] Schedule of Changes in Projected Benefit Obligations Changes in Projected Benefit Obligations, Fair Value of Plan Assets, and Funded Status of Plan [Table Text Block] Segment Reporting Information [Line Items] Segment Reporting Information [Line Items] Disposal Group Name Disposal Group Name [Axis] Compensation and Retirement Disclosure [Line Items] Compensation And Retirement Disclosure [Line Items] Compensation and retirement disclosure. Lease cost Total lease cost, net Lease, Cost Leases Lessee Operating And Finance Lease Disclosure [Text Block] The entire disclosure for operating lease and finance lease by the lessee. Payments for (Proceeds from) Sale of Operations Payments for (Proceeds from) Sale of Operations Net proceeds from sale of operations Other jurisdictions, Tax expense Other jurisdictions, Tax expense Other jurisdictions Current Other Jurisdictions Tax Expense Benefit Current other jurisdictions tax expense benefit. Software [Member] Computer Software, Intangible Asset [Member] Cash and Cash Equivalents Cash and Cash Equivalents, Policy [Policy Text Block] Non-Fiduciary Cash [Member] Non-Fiduciary Cash [Member] Non-fiduciary cash member December Thirty One Two Thousand And Twenty Three [Member] December thirty one two thousand and twenty three. Dec 31, 2023 [Member] Business Combination, Consideration Transferred, Equity Interest Acquisiiton , equity payment Senior notes due 2048, 0505. 5.050% senior notes due 2048 [Member] Senior Notes Due20480505 [Member] Derivatives Derivative Liability, Current Property, Plant and Equipment, Net, Ending Balance Property, Plant and Equipment, Net, Beginning Balance Property, Plant and Equipment, Net, Total Fixed assets, net Property, Plant and Equipment, Net Defined Benefit Plan, Expected Future Benefit Payment, Year Three 2028 Defined benefit plan benefit obligation and addition disposal. Defined Benefit Plan Benefit Obligation And Addition Disposal Plan (disposal)/addition U.K. corporation tax Deferred Foreign Income Tax Expense (Benefit) Total cash, cash equivalents and restricted cash Cash, Cash Equivalent, Restricted Cash, and Restricted Cash Equivalent, Including Discontinued Operation Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents, Including Disposal Group and Discontinued Operations, Ending Balance Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents, Including Disposal Group and Discontinued Operations, Beginning Balance Income from operations Operating Income (Loss) Income from operations Segment operating income Foreign exchange Goodwill, Foreign Currency Translation, Gain (Loss) Capitalized Contract Cost [Table] Summary of Income Tax Examinations Summary of Income Tax Examinations [Table Text Block] Revenue and Tangible Long-lived Assets by Geographical Areas Schedule of Revenue from External Customers and Long-Lived Assets, by Geographical Areas [Table Text Block] Ordinary shares, $0.000304635 nominal value [Member] Ordinary Share One [Member] Ordinary share one. Derivative Instruments, Gain (Loss) Reclassification from Accumulated OCI to Income, Estimated Net Amount to be Transferred Gains on derivatives to be reclassified within the next twelve months Retained Earnings [Member] Retained earnings/(accumulated deficit) [Member] Entity Address, Country Entity Address, Country Business Combination, Contingent Consideration, Type [Domain] Cash and Cash Equivalents [Axis] Projected benefit obligation at end of year Defined Benefit Plan, Pension Plan with Accumulated Benefit Obligation in Excess of Plan Assets, Projected Benefit Obligation Total non-current assets Assets, Noncurrent Share-based Payment Arrangement, Noncash Expense, Total Share-based compensation Share-Based Payment Arrangement, Noncash Expense Salaries and Benefits [Member] Salaries And Benefits [Member] Salaries and benefits. Total non-current liabilities Liabilities, Noncurrent Operating Leases, Weighted-average discount rate Operating Lease, Weighted Average Discount Rate, Percent Operating Lease, Long-term lease liabilities Long-term lease liabilities Operating Lease, Liability, Noncurrent Level 1 [Member] Fair Value, Inputs, Level 1 [Member] Risk-Free Rate [Member] Risk-free rate. Risk-Free Rate [Member] Net cash used in financing activities Cash Provided by (Used in) Financing Activity, Including Discontinued Operation Schedule of Amount Recorded in Consolidated Statements of Comprehensive Income Lease, Cost [Table Text Block] Discount rate - PBO Defined Benefit Plan Assumptions Used Calculating Net Periodic Benefit Cost Discount Rate Projected Benefit Obligation Defined benefit plan, assumptions used calculating net periodic benefit cost, discount rate, projected benefit obligation. Foreign currency translation [Member] Accumulated Foreign Currency Adjustment Including Portion Attributable to Noncontrolling Interest [Member] Auditor Location Revenue Commissioners, Ireland [Member] Revenue Commissioners, Ireland [Member] Amortization of unrecognized actuarial loss Other Comprehensive Income (Loss), Defined Benefit Plan, Gain (Loss), Reclassification Adjustment from AOCI, before Tax Provisions for Liabilities Provisions For Liabilities Table [Text Block] Provisions for liabilities. Schedule of Other Current Assets [Table Text Block] Schedule of Prepaid and Other Current Assets Restructuring Charges [Member] Restructuring Charges [Member] Total Restructuring Costs [Member] Bain Capital Joint Venture [Member] Bain Capital Joint Venture. Bain Capital Joint Venture Derivative Contract Derivative Contract [Domain] Willis Limited [Member] Willis Limited [Member] Willis limited. Defined Benefit Plan Payable Receivable For Interest Income And Other Defined benefit plan (payable) receivable for interest income and other. Receivable for interest income and other Income From Continuing Operations Before Income Taxes And Interest In Earnings Of Associates [Table] Income From Continuing Operations Before Income Taxes And Interest In Earnings Of Associates [Table] Income from continuing operations before income taxes and interest in earnings of associates. Schedule Of Goodwill [Table] Goodwill [Table] Foreign exchange Finite-Lived Intangible Assets, Foreign Currency Translation Gain (Loss) Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items] Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items] Defined Contribution Plan Tranche One [Member] Defined Contribution Plan Tranche One [Member] Defined contribution plan tranche one. Non-US [Member] Non-US [Member] Longest outstanding maturity Derivative, Remaining Maturity Corporate bonds [Member] Corporate Debt Securities [Member] Corporate Debt Securities [Member] Income Tax Authority Income Tax Jurisdiction [Domain] Entity Interactive Data Current Entity Interactive Data Current Willis North America Inc [Member] Willis North America Inc [Member] Willis north america inc. Defined Benefit Plan, Plan Assets, Category Defined Benefit Plan, Plan Assets, Category [Axis] Income Statement Location Statement of Income Location, Balance [Domain] Fair Value Measurement Fair Value Measurement [Domain] CASH FLOWS FROM OPERATING ACTIVITIES Cash Provided by (Used in) Operating Activity, Including Discontinued Operation [Abstract] Furniture, equipment and software [Member] Furniture and Fixtures [Member] Net payments on revolving credit facility Repayment of line of credit Repayments of Lines of Credit Schedule of Lease Schedule Of Lease Table [Text Block] Schedule of lease. Time based RSUs Generally Vest [Member] Time based RSUs generally vest. Time-based RSUs Generally Vest [Member] Her Majesty's Revenue and Customs (HMRC) [Member] His Majesty's Revenue and Customs (HMRC) [Member] Prepayments and accrued income Prepaid Expense And Accrued Revenue Receivable Current Prepaid expense and accrue revenue receivable current. Movement in Valuation Allowances and Reserves [Roll Forward] SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward] Unbilled Receivables, Current Unbilled Receivable, Current Unrecognized Tax Benefits, Income Tax Penalties Accrued Accrued penalties Net carrying amount Debt Securities, Held-to-Maturity, Amortized Cost, after Allowance for Credit Loss Costs Recognized In Net Periodic Benefit Cost And Other Comprehensive Income Costs Recognized in Net Periodic Benefit Cost and Other Comprehensive Income Total recognized in net periodic benefit cost/(credit) and other comprehensive loss/(income) Realized and unrealized losses Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Gain (Loss) Included in Earnings Deferred tax liabilities: Components of Deferred Tax Liabilities [Abstract] Dividends declared per share Common Stock, Dividends, Per Share, Declared Tax benefit from compensation expense Share-Based Payment Arrangement, Expense, Tax Benefit Entity Tax Identification Number Entity Tax Identification Number EQUITY Equity, Including Portion Attributable to Noncontrolling Interest [Abstract] Long-term Debt, Type Long-Term Debt, Type [Axis] Earnout receivable Business Combination, Contingent Consideration, Asset, Current Other [Member] Other Investments [Member] Debt instrument, term Debt Instrument, Term Risk and Broking. Risk and Broking [Member] R&B [Member] Income from Operations Before Income Loss from Equity Method Investments Income from operations before income loss from equity method investments. INCOME/(LOSS) FROM OPERATIONS BEFORE INTEREST IN EARNINGS OF ASSOCIATES INCOME/(LOSS) FROM OPERATIONS BEFORE INTEREST IN EARNINGS OF ASSOCIATES Income Tax Authority, Name Income Tax Authority, Name [Domain] Effect of exchange rate changes on cash, cash equivalents and restricted cash Effect of Exchange Rate on Cash, Cash Equivalent, Restricted Cash, and Restricted Cash Equivalent, Continuing Operation Miller [Member] Miller [Member] Miller. Cash flows used in financing activities: Cash Flow, Financing Activities, Lessee [Abstract] Third-party commissions Accrued Sales Commission, Current Local Phone Number Local Phone Number EURO-Denominated [Member] E U R O Denominated [Member] EURO-denominated. Accumulated Other Comprehensive Income (Loss) [Line Items] Accumulated Other Comprehensive Income (Loss) [Line Items] Defined Benefit Plan, Net Periodic Benefit Cost (Credit) Net periodic benefit cost/(credit) Total other current liabilities Other current liabilities Other Liabilities, Current Short-term lease cost Short-Term Lease, Cost Auditor Opinion [Text Block] Auditor Opinion [Text Block] Total Restructuring Costs Restructuring Costs, Total Finance Lease, Liability, to be Paid, Year Two Finance Lease, 2027 Contract with Customer, Asset, after Allowance for Credit Loss, Noncurrent, Total Non-current contract assets Contract with Customer, Asset, after Allowance for Credit Loss, Noncurrent Non-current contract assets Long-Lived Assets Long-Lived Assets Schedule of Changes in Allowance for Doubtful Accounts Financing Receivable, Current, Allowance for Credit Loss [Table Text Block] Time based RSUs Immediately Vest [Member] Time based RSUs immediately vest. Time-based RSUs Immediately Vest [Member] Cash acquired Cash Acquired from Acquisition U.S. Federal and Non-U.S. [Member] Federal And Foreign Tax Authority [Member] Federal and foreign tax authority. Tax expense includes in interest expense Unrecognized Tax Benefits, Interest on Income Taxes Expense Accounting Policies [Abstract] Contract with Customer, Performance Obligation Satisfied in Previous Period Contract with Customer, Performance Obligation Satisfied in Previous Period Disaggregation Of Revenue [Line Items] Disaggregation of Revenue [Line Items] Tax on unremitted earnings Tax on unremitted earnings net of foreign tax credits. Tax On Unremitted Earnings Net Of Foreign Tax Credits Tax on unremitted earnings Other current liabilities Other Sundry Liabilities, Current Deferred Tax Liabilities, Undistributed Foreign Earnings Unremitted earnings Unremitted earnings Revenue from Contract with Customer, Excluding Assessed Tax, Total Revenue from Contract with Customer, Excluding Assessed Tax Revenue from Contract with Customer, Excluding Assessed Tax Investment in multiple employer pension plan [Member] Investment in multiple employer pension plan. Schedule of Other Non-current Assets Schedule of Other Assets, Noncurrent [Table Text Block] Lessee, Operating Lease, Liability, to be Paid, Year Four Operating Lease, 2029 Cash [Member] Cash and Cash Equivalents [Member] Class of Stock [Domain] Class of Stock State Apportionment [Member] State Apportionment [Member] State apportionment. Salaries and benefits Labor and Related Expense Number of shares available for grant Share-Based Compensation Arrangement by Share-Based Payment Award, Number of Shares Available for Grant Compensation cost not yet recognized, period for recognition Share-Based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Period for Recognition Maximum annual contributions per employee, percent Defined Contribution Plan, Maximum Annual Contributions Per Employee, Percent Capitalized Contract Cost [Domain] Deferred Revenue and Accrued Expenses Schedule of Accounts Payable and Accrued Liabilities [Table Text Block] Health, Wealth and Career Health, Wealth and Career [Member] HWC [Member] Broking Business [Member] Broking business. Broking Business [Member] Accumulated impairment losses, beginning balance Accumulated impairment losses, ending balance Goodwill, Impaired, Accumulated Impairment Loss Entity Emerging Growth Company Entity Emerging Growth Company Disposal Group, Including Discontinued Operation, Operating Income (Loss) Operating Income