Dividends (in dollars per share) Common Stock, Dividends, Per Share, Cash Paid Accumulated Amortization and Impairment Finite-Lived Intangible Assets, Accumulated Amortization Accounting Principles and Practices Significant Accounting Policies [Text Block] Accelerating Aon United Program liabilities Increase (Decrease) in Restructuring Reserve Statistical Measurement [Domain] Statistical Measurement [Domain] Other Current Assets Other Current Assets [Member] Capitalized Contract Cost [Axis] Capitalized Contract Cost [Axis] Expected return on plan assets, net of administration expenses Defined Benefit Plan, Expected Return (Loss) on Plan Assets Additions Capitalized Contract Cost, Additions Capitalized Contract Cost, Additions Current portion of long-term debt, fair value Short-Term Debt, Fair Value Foreign Plan Foreign Plan [Member] Award Timing Predetermined Award Timing Predetermined [Flag] Entity File Number Entity File Number Other Noncurrent Assets Other Noncurrent Assets [Member] Guarantees of Aon Corporation and Aon Global Holdings plc’s 2.050% Senior Notes due 2031 Guarantees Of Aon Plc's 2.050% Senior Notes Due 2031 [Member] Guarantees Of Aon Plc's 2.050% Senior Notes Due 2031 Equity loss Income (Loss) from Equity Method Investments Tabular List, Table Tabular List [Table Text Block] Other Financial Data Additional Financial Information Disclosure [Text Block] Schedule of Other Non-current Liabilities Other Noncurrent Liabilities [Table Text Block] New Accounting Pronouncements New Accounting Pronouncements, Policy [Policy Text Block] Sale of businesses, net of cash and funds held on behalf of clients Proceeds from Divestiture of Businesses, Net of Cash Divested Cost to fulfill contracts with customers Contract with Customer, Asset, after Allowance for Credit Loss, Current Schedule of Financial Instruments Where the Carrying Amounts and Fair Values Differ Fair Value, by Balance Sheet Grouping [Table Text Block] Deferred and contingent consideration Business Combination, Consideration Transferred, Liabilities Incurred Type of Restructuring [Domain] Type of Restructuring [Domain] Maximum potential funding under commitments Guarantor Obligations, Maximum Exposure, Undiscounted Goodwill [Line Items] Goodwill [Line Items] Trading Arrangements, by Individual Trading Arrangements, by Individual [Table] Other expenses Other Expenses Measurement Basis [Axis] Measurement Basis [Axis] Basic net income per share attributable to Aon shareholders (in dollars per share) Earnings Per Share, Basic Adjustment to Compensation: Adjustment to Compensation [Axis] Named Executive Officers, Footnote Named Executive Officers, Footnote [Text Block] Commercial paper Commercial Paper [Member] Accounts payable and accrued liabilities Increase (Decrease) in Accounts Payable and Accrued Liabilities Liabilities Liabilities, Fair Value Disclosure [Abstract] Other Other Assets, Miscellaneous, Current Revenue from Contracts with Customers Revenue from Contract with Customer [Text Block] Consideration transferred: Business Combination, Consideration Transferred [Abstract] Total other comprehensive income (loss) Other Comprehensive Income (Loss), Net of Tax Schedule of Reportable Operating Segments, Consolidated Revenue and Segment Operating Income Schedule of Segment Reporting Information, by Segment [Table Text Block] Commercial paper outstanding Short-Term Debt Capitalized Cost To Obtain Customer Contracts Capitalized Cost To Obtain Customer Contracts [Member] Capitalized Cost To Obtain Customer Contracts [Member] Pension, other postretirement, and postemployment liabilities Liability, Pension and Other Postretirement and Postemployment Benefits, Noncurrent Other Other Assets, Miscellaneous, Noncurrent Capitalized Contract Cost [Domain] Capitalized Contract Cost [Domain] Adjustment to Compensation, Amount Adjustment to Compensation Amount Consolidation Consolidation, Policy [Policy Text Block] Share-based compensation expense Share-Based Payment Arrangement, Noncash Expense Damages sought option 1 Loss Contingency, Damages Sought, Value, Option One Loss Contingency, Damages Sought, Value, Option One Employee Stock Option Share-Based Payment Arrangement, Option [Member] Award Timing MNPI Disclosure Award Timing MNPI Disclosure [Text Block] Number of credit facilities Number Of Credit Facilities Number Of Credit Facilities Cash and Cash Equivalents and Short-Term Investments Cash, Cash Equivalent, and Short-Term Investment [Text Block] Dividends to shareholders Dividends, Common Stock, Cash Total Aon shareholders' equity Equity, Attributable to Parent Other comprehensive income (loss), net of tax: Other Comprehensive Income (Loss), Net of Tax [Abstract] Insider Trading Policies and Procedures [Line Items] Ordinary shares, authorized shares (in shares) Common Stock, Shares Authorized Hedging Designation [Domain] Hedging Designation [Domain] Workforce optimization Workforce Optimization [Member] Workforce Optimization Goodwill and Intangible Assets Disclosure [Abstract] Goodwill and Intangible Assets Disclosure [Abstract] Current assets Assets, Current [Abstract] Total liabilities, redeemable noncontrolling interests and equity Liabilities and Equity Postretirement Benefit Obligation Accumulated Defined Benefit Plans Adjustment Attributable to Parent [Member] Cash, cash equivalents and funds held on behalf of clients at beginning of period Cash, cash equivalents and funds held on behalf of clients at end of period Total cash and cash equivalents and funds held on behalf of clients Cash, Cash Equivalent, Restricted Cash, and Restricted Cash Equivalent, Including Discontinued Operation Liabilities, redeemable noncontrolling interests, and equity Liabilities and Equity [Abstract] Cover [Abstract] Cover [Abstract] Portion at Fair Value Measurement Portion at Fair Value Measurement [Member] Maximum Maximum [Member] Less: Net income attributable to redeemable and nonredeemable noncontrolling interests Less: Net income attributable to redeemable and nonredeemable noncontrolling interests Net Income (Loss) Attributable to Noncontrolling Interest Accounting Policies [Abstract] Accounting Policies [Abstract] Intangible assets, net Total Finite-Lived Intangible Assets, Net Non-PEO NEO Average Total Compensation Amount Non-PEO NEO Average Total Compensation Amount Debt Instrument [Line Items] Debt Instrument [Line Items] Purchases of investments Payments to Acquire Other Investments Adjustment to Non-PEO NEO Compensation Footnote Adjustment to Non-PEO NEO Compensation Footnote [Text Block] Pay vs Performance Disclosure [Line Items] Retirement Benefits [Abstract] Retirement Benefits [Abstract] Forgone Recovery due to Disqualification of Tax Benefits, Amount Forgone Recovery due to Disqualification of Tax Benefits, Amount Damages sought option 2 Loss Contingency, Damages Sought, Value, Option Two Loss Contingency, Damages Sought, Value, Option Two Liabilities Liabilities [Abstract] Non-Rule 10b5-1 Arrangement Terminated Non-Rule 10b5-1 Arrangement Terminated [Flag] Income before income taxes Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest Entity Shell Company Entity Shell Company Other non-current liabilities Total Other Liabilities, Noncurrent Schedule of Long-term Debt Instruments [Table] Schedule of Long-Term Debt Instruments [Table] Number of dispositions Number Of Dispositions Represents the number of entities disposed of by the reporting entity. Statement of Stockholders' Equity [Abstract] Statement of Stockholders' Equity [Abstract] Operating Segments Operating Segments [Member] Other general expense Other General Expenses General recurring costs associated with normal operations, excluding compensation and benefits. Current portion of long-term debt Long-Term Debt, Current Maturities Statement of Cash Flows [Abstract] Statement of Cash Flows [Abstract] Company Selected Measure Amount Company Selected Measure Amount Company’s benefit pension plans Defined Benefit Plan, Plan Assets, Contributions by Employer Award Timing MNPI Considered Award Timing MNPI Considered [Flag] Comprehensive income attributable to Aon shareholders Comprehensive Income (Loss), Net of Tax, Attributable to Parent Schedule of Other Current Assets Schedule of Other Current Assets [Table Text Block] Disposal Group Name [Domain] Disposal Group Name [Domain] Name Measure Name Liability balance as of December 31, 2025 Liability balance as of March 31, 2026 Restructuring Reserve Weighted average commercial paper outstanding Short-Term Debt, Average Outstanding Amount Taxes payable Accrued Income Taxes, Noncurrent Movement ofAccounts Receivable, Allowance for Credit Loss, Current [Roll Forward] Movement of Accounts Receivable, Allowance for Credit Loss, Current [Roll Forward] Movement of Accounts Receivable, Allowance for Credit Loss, Current Deferred tax liabilities Deferred Income Tax Liabilities, Net Document Fiscal Period Focus Document Fiscal Period Focus Award Timing Method Award Timing Method [Text Block] Litigation Case [Domain] Litigation Case [Domain] Customer-related and contract-based Customer Related And Contract Based [Member] Represents finite-lived intangible assets such as client lists and non-compete agreements. Award Type Award Type [Axis] Deferred revenue Contract with Customer, Liability, Noncurrent Hedging Relationship [Domain] Hedging Relationship [Domain] Foreign Currency Translation Adjustments Accumulated Foreign Currency Adjustment Attributable to Parent [Member] Nonredeemable noncontrolling interests Nonredeemable Noncontrolling Interest Total assets Assets 2027 Finite-Lived Intangible Asset, Expected Amortization, Year One Trading Symbol Trading Symbol Geographical [Domain] Geographical [Domain] Shares issued - employee stock compensation plans (in shares) Shares Issued, Shares, Share-Based Payment Arrangement, after Forfeiture Entity Address, City or Town Entity Address, City or Town Short-term Debt, Type [Domain] Short-Term Debt, Type [Domain] Cash flows from operating activities Cash Provided by (Used in) Operating Activity, Including Discontinued Operation [Abstract] Wealth Solutions Wealth Solutions [Member] Wealth Solutions European Program European Multi-Currency Commercial Paper Program [Member] European Multi-Currency Commercial Paper Program [Member] Effect of exchange rates on cash and cash equivalents and funds held on behalf of clients Effect of Exchange Rate on Cash, Cash Equivalent, Restricted Cash, and Restricted Cash Equivalent, Continuing Operation Non-PEO NEO Average Compensation Actually Paid Amount Non-PEO NEO Average Compensation Actually Paid Amount Statement of Income Location, Balance [Domain] Statement of Income Location, Balance [Domain] Compensation Actually Paid vs. Other Measure Compensation Actually Paid vs. Other Measure [Text Block] Aggregate consideration transferred Business Combination, Consideration Transferred Assets Assets, Fair Value Disclosure [Abstract] 2030 Finite-Lived Intangible Asset, Expected Amortization, Year Four Entity Emerging Growth Company Entity Emerging Growth Company Capitalized Contract Cost [Table] Capitalized Contract Cost [Table] Other investments Other Investments Dividends payable (in dollars per share) Common Stock, Dividends, Per Share, Declared Entity Common Stock, Shares Outstanding Entity Common Stock, Shares Outstanding Balance at beginning of period Balance at end of period Capitalized Contract Cost, Net Cash, Cash Equivalents, and Short-term Investments [Abstract] Cash, Cash Equivalents, and Short-Term Investments [Abstract] Pension, other postretirement and postemployment liabilities Increase (Decrease) in Obligation, Pension and Other Postretirement Benefits Change in Fair Value as of Vesting Date of Prior Year Equity Awards Vested in Covered Year Change in Fair Value as of Vesting Date of Prior Year Equity Awards Vested in Covered Year [Member] Significant Other Observable Inputs (Level 2) Fair Value, Inputs, Level 2 Fair Value, Inputs, Level 2 [Member] Gain (loss) on derivative Derivative, Gain (Loss) on Derivative, Net Revenue recognized from deferred revenue Contract with Customer, Liability, Including New Contract Revenue Recognized Contract with Customer, Liability, Including New Contract Revenue Recognized Restructuring Reserve [Roll Forward] Restructuring Reserve [Roll Forward] Insider Trading Policies and Procedures Not Adopted Insider Trading Policies and Procedures Not Adopted [Text Block] Business Combination [Domain] Business Combination [Domain] Pre-tax gain Disposal Group, Not Discontinued Operation, Gain (Loss) on Disposal Provision Accounts Receivable, Credit Loss Expense (Reversal) PEO PEO [Member] Schedule of Disaggregation of Revenue Disaggregation of Revenue [Table Text Block] Prepaid pension Assets for Plan Benefits, Defined Benefit Plan Taxes payable Accrued Income Taxes, Current U.S. U.S. U.S. UNITED STATES Change in assets and liabilities: Adjustment to Reconcile Net Income to Cash Provided by (Used in) Operating Activity, Increase (Decrease) in Operating Capital [Abstract] Dividends or Other Earnings Paid on Equity Awards not Otherwise Reflected in Total Compensation for Covered Year Dividends or Other Earnings Paid on Equity Awards not Otherwise Reflected in Total Compensation for Covered Year [Member] Schedule of Estimated Future Amortization Expense on Intangible Assets Schedule of Finite-Lived Intangible Assets, Future Amortization Expense [Table Text Block] Derivative Instruments and Hedging Activities Disclosure [Abstract] Derivative Instruments and Hedging Activities Disclosure [Abstract] Retained Earnings (Accumulated Deficit) Retained Earnings [Member] Entity Address, Postal Zip Code Entity Address, Postal Zip Code Restatement Determination Date Restatement Determination Date Consolidated Statements of Income Income Statement [Abstract] Derivatives Derivative Asset Income tax expense Income Tax Expense (Benefit) Pension Adjustments Service Cost Pension Adjustments Service Cost [Member] Accounted for as hedges Designated as Hedging Instrument [Member] Guarantees of Aon North America, Inc.’s 5.125% Senior Notes due 2027 Guarantees Of Aon North America, Inc.’s 5.125% Senior Notes Due 2027 [Member] Guarantees Of Aon North America, Inc.’s 5.125% Senior Notes Due 2027 Product and Service [Domain] Product and Service [Domain] Fair Value Hierarchy and NAV [Axis] Fair Value Hierarchy and NAV [Axis] Hedging Relationship [Axis] Hedging Relationship [Axis] Schedule of Capitalized Contract Cost Capitalized Contract Cost [Table Text Block] Net income Net income Net Income (Loss), Including Portion Attributable to Noncontrolling Interest Accelerating Aon United Program Accelerating Aon United Program [Member] Accelerating Aon United Program Restatement does not require Recovery Restatement Does Not Require Recovery [Text Block] Business Combination [Table] Business Combination [Table] Expected cost, cash charges Restructuring And Related Cost, Expected Cost, Cash Charges Restructuring And Related Cost, Expected Cost, Cash Charges Notional Amount Derivative, Notional Amount Organization, Consolidation and Presentation of Financial Statements [Abstract] Organization, Consolidation and Presentation of Financial Statements [Abstract] Accelerating Aon United Program Restructuring and Related Activities Disclosure [Text Block] Schedule of Consideration Transferred and Preliminary Value of Intangible Assets Business Combination, Recognized Asset Acquired and Liability Assumed [Table Text Block] Compensation Actually Paid vs. Company Selected Measure Compensation Actually Paid vs. Company Selected Measure [Text Block] Goodwill related to current year acquisitions Goodwill, Acquired During Period City Area Code City Area Code Acquisitions and Dispositions of Businesses Mergers, Acquisitions and Dispositions Disclosures [Text Block] Acquisition of businesses, net of cash and funds held on behalf of clients Payments to Acquire Businesses, Net of Cash Acquired Award Timing, How MNPI Considered Award Timing, How MNPI Considered [Text Block] All Trading Arrangements All Trading Arrangements [Member] Equity Awards Adjustments, Footnote Equity Awards Adjustments, Footnote [Text Block] Total Shareholder Return Vs Peer Group Total Shareholder Return Vs Peer Group [Text Block] Foreign currency exposures, maximum average hedging period (less than) (in years) Maximum Average Maturity of Foreign Currency Derivatives Maximum average contract period for foreign currency exchange rate derivatives. Commitments and Contingencies Disclosure [Abstract] Commitments and Contingencies Disclosure [Abstract] Proceeds from long-term lines of credit Proceeds from Long-Term Lines of Credit Cash flows from investing activities Cash Provided by (Used in) Investing Activity, Including Discontinued Operation [Abstract] Pay vs Performance Disclosure Pay vs Performance Disclosure [Table] Cash provided by operating activities Cash Provided by (Used in) Operating Activity, Including Discontinued Operation Disposal Group, Disposed of by Sale, Not Discontinued Operations Disposal Group, Disposed of by Sale, Not Discontinued Operations [Member] Investments Long-Term Investments Amortization of net actuarial loss Defined Benefit Plan, Amortization of Gain (Loss) Subsequent Event Subsequent Event [Member] Other assets Business Combination, Recognized Asset Acquired, Other Asset, Current Cash Flow Hedging Cash Flow Hedging [Member] Goodwill Beginning balance Ending balance Goodwill Equity Valuation Assumption Difference, Footnote Equity Valuation Assumption Difference, Footnote [Text Block] PEO Total Compensation Amount PEO Total Compensation Amount Long-term Debt, Type [Axis] Long-Term Debt, Type [Axis] Depreciation of fixed assets Depreciation of fixed assets Depreciation NFP Wealth NFP Wealth [Member] NFP Wealth Guarantees of Aon North America, Inc.’s 5.750% Senior Notes due 2054 Guarantees Of Aon North America, Inc.’s 5.750% Senior Notes Due 2054 [Member] Guarantees Of Aon North America, Inc.’s 5.750% Senior Notes Due 2054 Cash and cash equivalents and short-term investments Cash And Cash Equivalents And Short-Term Investments Cash And Cash Equivalents And Short-Term Investments Net amount of derivative liabilities Derivative Liability, Subject to Master Netting Arrangement, before Offset Remainder of 2026 Finite-Lived Intangible Asset, Expected Amortization, Remainder of Fiscal Year Assets acquired: Business Combination, Recognized Asset Acquired, Asset [Abstract] Equity Components [Axis] Equity Components [Axis] Remeasurement of redemption value of redeemable noncontrolling interest Noncontrolling Interest, Change in Redemption Value Non-Rule 10b5-1 Arrangement Adopted Non-Rule 10b5-1 Arrangement Adopted [Flag] Number of reportable segment Number of Reportable Segments Total revenue Sales [Member] Supplemental disclosures: Supplemental Cash Flow Information [Abstract] Restructuring Cost and Reserve [Line Items] Restructuring Cost and Reserve [Line Items] Entity Address, Country Entity Address, Country Other Performance Measure, Amount Other Performance Measure, Amount Short-term debt and current portion of long-term debt Debt, Current Delayed draw term loan Delayed Draw Term Loan (DDTL) [Member] Fair Value Measurements and Financial Instruments Fair Value Measurement, Policy [Policy Text Block] Total current liabilities Liabilities, Current Other Current Liabilities Other Current Liabilities [Member] Litigation Status [Axis] Litigation Status [Axis] Derivative Instrument [Axis] Derivative Instrument [Axis] Total costs incurred from inception to date Restructuring and Related Cost, Cost Incurred to Date Individual: Individual [Axis] Cash dividends to shareholders Payments of Ordinary Dividends, Common Stock Other current assets Total Other Assets, Current Additional paid-in capital Additional Paid in Capital, Common Stock Entities [Table] Entities [Table] Cash provided by (used for) investing activities Cash Provided by (Used in) Investing Activity, Including Discontinued Operation Aggregate Change in Present Value of Accumulated Benefit for All Pension Plans Reported in Summary Compensation Table Aggregate Change in Present Value of Accumulated Benefit for All Pension Plans Reported in Summary Compensation Table [Member] Gain from sales of businesses Gain from disposals of businesses Gain (Loss) on Disposition of Business Interest paid Interest Paid, Excluding Capitalized Interest, Operating Activity Document Fiscal Year Focus Document Fiscal Year Focus Basis of Presentation Basis of Accounting, Policy [Policy Text Block] ShoreOne Insurance Managers, Inc. ShoreOne Insurance Managers, Inc. [Member] ShoreOne Insurance Managers, Inc. Operating lease right-of-use assets Operating Lease, Right-of-Use Asset Forgone Recovery, Explanation of Impracticability Forgone Recovery, Explanation of Impracticability [Text Block] Repayment of debt Repayments of Long-Term Debt Fiduciary assets Fiduciary Assets. Amounts due from clients and insurance companies, along with short-term investments held by the entity that will be paid to clients and insurance companies, net of a reserve for doubtful accounts. Effective income tax rate Effective Income Tax Rate Reconciliation, Percent Entity Interactive Data Current Entity Interactive Data Current Share repurchase authorization amount, increase during period Stock Repurchase Program, Authorized Amount, Increase During Period Stock Repurchase Program, Authorized Amount, Increase During Period Carrying Value Reported Value Measurement [Member] Equity [Abstract] Equity [Abstract] Restricted cash and investments Restricted Cash and Investments, Current Derivatives and Hedging Derivatives, Policy [Policy Text Block] Segment Information Segment Reporting Disclosure [Text Block] Operating margin Operating Margin Percentage Operating Margin Percentage Other Other International Plan [Member] Other International Plan [Member] Goodwill [Table] Goodwill [Table] 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] Not designated as hedging instrument Not accounted for as hedges Not Designated as Hedging Instrument [Member] Disaggregation of Revenue [Table] Disaggregation of Revenue [Table] Weighted average interest rate of commercial paper outstanding Short Term Debt, Average Outstanding Amount, Weighted Average Interest Rate Reflects the calculation as of the balance sheet date of the average interest rate weighted by the average outstanding amount of short-term debt outstanding by type or by instrument at that time. Increase (Decrease) in Stockholders' Equity [Roll Forward] Increase (Decrease) in Stockholders' Equity [Roll Forward] Information technology Information Technology and Data Processing Retirement Plan Sponsor Location [Axis] Retirement Plan Sponsor Location [Axis] Credit facility expiring september 2027 Credit Facility Expiring September 2027 [Member] Credit Facility Expiring September 2027 Finite-Lived Intangible Assets [Line Items] Finite-Lived Intangible Assets [Line Items] Schedule of Components of Net Periodic Benefit Cost for the Pension Plans Schedule of Net Benefit Costs [Table Text Block] Deferred consideration on divestiture Deferred Consideration On Divestiture Deferred Consideration On Divestiture Compensation Actually Paid vs. Total Shareholder Return Compensation Actually Paid vs. Total Shareholder Return [Text Block] Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Table] Fair Value, Recurring and Nonrecurring [Table] Fair Value, Recurring and Nonrecurring [Table] Gain on disposition of business Gain On Disposition of Business Gain On Disposition of Business Deferred tax assets Deferred Income Tax Assets, Net Schedule of Components of Accumulated Other Comprehensive Loss, Net of Related Tax Schedule of Accumulated Other Comprehensive Income (Loss) [Table Text Block] Other non-current assets Total Other Assets, Noncurrent Entity Central Index Key Entity Central Index Key Expected cost, non-cash charges Restructuring And Related Cost, Expected Cost, Non-Cash Charges Restructuring And Related Cost, Expected Cost, Non-Cash Charges PEO Name PEO Name Share repurchase Payments for Repurchase of Equity Prior Year End Fair Value of Equity Awards Granted in Any Prior Year that Fail to Meet Applicable Vesting Conditions During Covered Year Prior Year End Fair Value of Equity Awards Granted in Any Prior Year that Fail to Meet Applicable Vesting Conditions During Covered Year [Member] Damages sought option 3 Loss Contingency, Damages Sought, Value, Option Three Loss Contingency, Damages Sought, Value, Option Three Europe, Middle East, & Africa other than U.K. and Ireland Europe, Middle East, And Africa, Other Than United Kingdom And Ireland [Member] Europe, Middle East, And Africa, Other Than United Kingdom And Ireland Outstanding Aggregate Erroneous Compensation Amount Outstanding Aggregate Erroneous Compensation Amount Foreign currency translation and other Accounts Receivable, Allowance For Credit Loss, Foreign Currency Translation And Other Accounts Receivable, Allowance For Credit Loss, Foreign Currency Translation And Other Schedule of Defined Benefit Plans Disclosures [Table] Defined Benefit Plan [Table] Contingent consideration Business Combination, Contingent Consideration, Liability, Noncurrent Arrangement Duration Trading Arrangement Duration Schedule of Segment Reporting Information, by Segment [Table] Schedule of Segment Reporting Information, by Segment [Table] Risk Capital Risk Capital Risk Capital Segment [Member] Risk Capital Segment Deferred revenue Contract with Customer, Liability, Current Segments [Axis] Segments [Axis] Exercise Price Award Exercise Price Entity Filer Category Entity Filer Category Local Phone Number Local Phone Number Class of Stock [Domain] Class of Stock [Domain] Additional 402(v) Disclosure Additional 402(v) Disclosure [Text Block] Cost to obtain contracts with customers Contract with Customer, Asset, after Allowance for Credit Loss, Noncurrent Asset impairments Asset Impairments [Member] Asset Impairments Subsequent Event Type [Axis] Subsequent Event Type [Axis] Contingent consideration Business Combination, Contingent Consideration, Liability, Current Shares repurchased (in shares) Shares purchased (in shares) Stock Repurchased and Retired During Period, Shares Fiduciary liabilities Fiduciary Liabilities Carrying value as of the balance sheet date of Insurance premiums payable and claims payable. Insurance premiums payable represent premiums collected from insured's and, after deducting the reporting entity's commissions, are due to the respective insurers. Claims payable represent claim payments received from the respective insurers and due to the insured. These unremitted insurance premiums and claims are held in a fiduciary capacity. Intangible assets Business Combination, Recognized Asset Acquired, Identifiable Intangible Asset, Excluding Goodwill Corporate/Eliminations Corporate And Eliminations [Member] Corporate And Eliminations Cash and cash equivalents Business Combination, Recognized Asset Acquired, Cash and Cash Equivalent Purchase price Disposal Group, Including Discontinued Operation, Consideration Expected cost Restructuring and Related Cost, Expected Cost Assets Assets [Abstract] Long-term debt Long-term debt Long-Term Debt, Excluding Current Maturities Credit Facility [Axis] Credit Facility [Axis] Underlying Security Market Price Change Underlying Security Market Price Change, Percent Balance Sheet Location [Axis] Statement of Financial Position Location, Balance [Axis] 2029 Finite-Lived Intangible Asset, Expected Amortization, Year Three Debt Instrument [Axis] Debt Instrument [Axis] Cash and cash equivalents and funds held on behalf of clients classified as held for sale Disposal Group, Including Discontinued Operation, Cash and Cash Equivalents Fair Value Measurements and Financial Instruments Fair Value Disclosures [Text Block] Employee Benefits Retirement Benefits [Text Block] Business Combination [Line Items] Business Combination [Line Items] Amounts reclassified from accumulated other comprehensive income (loss) Reclassification from Accumulated Other Comprehensive Income, Current Period, before Tax Credit Facility [Domain] Credit Facility [Domain] Gross Carrying Amount Finite-Lived Intangible Assets, Gross Vesting Date Fair Value of Equity Awards Granted and Vested in Covered Year Vesting Date Fair Value of Equity Awards Granted and Vested in Covered Year [Member] U.S. Program US Commercial Paper Program [Member] US Commercial Paper Program [Member] Entity Address, Address Line One Entity Address, Address Line One 3.875% Senior Notes due December 2025 3.875% Senior Notes Due December 2025 [Member] 3.875% Senior Notes due December 2025 [Member] Accumulated  Other Comprehensive Loss, Net of Tax AOCI Attributable to Parent AOCI Attributable to Parent [Member] Debt interest rate percentage Debt Instrument, Interest Rate, Stated Percentage Balance at beginning of period Balance at end of period Accounts Receivable, Allowance for Credit Loss, Current Non-current operating lease liabilities Operating Lease, Liability, Noncurrent Redeemable noncontrolling interests Redeemable Noncontrolling Interest, Equity, Carrying Amount Business Combination, Asset Acquisition, Transaction between Entities under Common Control, and Joint Venture Formation [Abstract] Derivatives and Hedging Derivative Instruments and Hedging Activities Disclosure [Text Block] Proceeds from investments Proceeds from Sale and Maturity of Other Investments Amortization of prior-service cost Defined Benefit Plan, Amortization of Prior Service Cost (Credit) Net amount of derivative assets Derivative Asset, Subject to Master Netting Arrangement, before Offset Dispositions Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items] Fair Value as of Grant Date Award Grant Date Fair Value Entity Registrant Name Entity Registrant Name Pretax gains that will be reclassified into earnings in the next twelve months Cash Flow Hedge Gain (Loss) to be Reclassified within 12 Months Guarantees of Aon North America, Inc.’s 5.450% Senior Notes due 2034 Guarantees Of Aon North America, Inc.’s 5.450% Senior Notes Due 2034 [Member] Guarantees Of Aon North America, Inc.’s 5.450% Senior Notes Due 2034 Stock Price or TSR Estimation Method Stock Price or TSR Estimation Method [Text Block] Net periodic cost (benefit) Defined Benefit Plan, Net Periodic Benefit Cost (Credit) Financial instruments and other Gain (Loss) On Financial Instruments And Other Gain (Loss) On Financial Instruments And Other Schedule of Other Income (Expense) Schedule of Other Nonoperating Income (Expense) [Table Text Block] Compensation and benefits Labor and Related Expense Dilutive effect of potentially issuable shares (in shares) Incremental Common Shares Attributable to Dilutive Effect of Share-Based Payment Arrangements Total operating expenses Costs and Expenses Document Quarterly Report Document Quarterly Report Deferred income taxes Deferred Income Taxes and Tax Credits Long term debt, fair value Long-Term Debt, Fair Value Changed Peer Group, Footnote Changed Peer Group, Footnote [Text Block] Foreign currency translation and other Capitalized Contract Cost, Foreign Currency And Other Adjustments Net Capitalized Contract Cost, Foreign Currency And Other Adjustments Net Adjustment To PEO Compensation, Footnote Adjustment To PEO Compensation, Footnote [Text Block] Interest cost Defined Benefit Plan, Interest Cost Title Trading Arrangement, Individual Title Peer Group Total Shareholder Return Amount Peer Group Total Shareholder Return Amount Guarantees of Aon North America, Inc.’s 5.300% Senior Notes due 2031 Guarantees Of Aon North America, Inc.’s 5.300% Senior Notes Due 2031 [Member] Guarantees Of Aon North America, Inc.’s 5.300% Senior Notes Due 2031 Other Noncurrent Liabilities Other Noncurrent Liabilities [Member] Schedule of Other Intangible Assets by Asset Class Schedule of Finite-Lived Intangible Assets [Table Text Block] Restatement Determination Date: Restatement Determination Date [Axis] Cash Payments to Acquire Businesses, Gross Shares issued - employee stock compensation plans Shares Issued, Value, Share-Based Payment Arrangement, after Forfeiture Non-PEO NEO Non-PEO NEO [Member] Letters of credit outstanding Letters of Credit Outstanding, Amount Accumulated Other Comprehensive Income (Loss) [Table] Accumulated Other Comprehensive Income (Loss) [Table] Schedule of Restructuring and Related Costs Restructuring and Related Costs [Table Text Block] Pension and other postretirement Pension Cost (Reversal Of Cost) And Other Postretirement Benefits Cost (Reversal Of Cost) Pension Cost (Reversal Of Cost) And Other Postretirement Benefits Cost (Reversal Of Cost) Schedule of Employer's Contributions Schedule Of Employer Contributions [Table Text Block] Schedule Of Employer Contributions [Table Text Block] Accumulated Other Comprehensive Income (Loss) [Line Items] Accumulated Other Comprehensive Income (Loss) [Line Items] Liabilities assumed: Business Combination, Recognized Liability Assumed, Liability [Abstract] Amounts reclassified from accumulated other comprehensive income (loss), net Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax Name Trading Arrangement, Individual Name Schedule of Share Repurchase Activity Schedule of Repurchase Agreements [Table Text Block] All Award Types Award Type [Domain] Gain recognized in Accumulated other comprehensive loss Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), before Reclassification and Tax Loss contingency, number of jurisdictions Loss Contingency, Number Of Jurisdictions Loss Contingency, Number Of Jurisdictions Equity Awards Adjustments Equity Awards Adjustments [Member] Other, net Other Noncash Income (Expense) Pension Benefits Adjustments, Footnote Pension Benefits Adjustments, Footnote [Text Block] Disaggregation of Revenue [Line Items] Disaggregation of Revenue [Line Items] Net purchases of subsidiary shares from nonredeemable noncontrolling interests Noncontrolling Interest, Decrease from Redemptions or Purchase of Interests Defined Benefit Plan Disclosure [Line Items] Defined Benefit Plan Disclosure [Line Items] Discontinued Operations, Disposed of by Sale Discontinued Operations, Disposed of by Sale [Member] Compensation Amount Outstanding Recovery Compensation Amount Debt, face amount Debt Instrument, Face Amount Debt Instrument, Name [Domain] Debt Instrument, Name [Domain] Litigation settlement expense Litigation Settlement, Fee Expense Leases Operating Lease And Finance Lease Liability, Current Operating Lease And Finance Lease Liability, Current Statement of Comprehensive Income [Abstract] Statement of Comprehensive Income [Abstract] Foreign exchange contracts Foreign Exchange Contract [Member] Recovery of Erroneously Awarded Compensation Disclosure [Line Items] Fair Value Estimate of Fair Value Measurement [Member] Schedule of Allowance for Doubtful Accounts Accounts Receivable, Allowance for Credit Loss [Table Text Block] MNPI Disclosure Timed for Compensation Value MNPI Disclosure Timed for Compensation Value [Flag] Compensation and benefits Employee-Related Liabilities, Noncurrent Employee-Related Liabilities, Noncurrent Name Awards Close in Time to MNPI Disclosures, Individual Name AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward] AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward] Americas other than U.S. Americas, Other Than United States [Member] Americas, Other than United States [Member] Accounts written off, net of recoveries Accounts Receivable, Allowance for Credit Loss, Write Off, Net Of Recoveries Accounts Receivable, Allowance for Credit Loss, Write Off, Net Of Recoveries Cash payments Payments for Restructuring Restructuring Type [Axis] Restructuring Type [Axis] Aggregate Erroneous Compensation Not Yet Determined Aggregate Erroneous Compensation Not Yet Determined [Text Block] Less: Other comprehensive income attributable to noncontrolling interests Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Noncontrolling Interest Revenue Revenues [Abstract] Other Other Accrued Liabilities, Noncurrent Share-based compensation expense APIC, Share-Based Payment Arrangement, Increase for Cost Recognition Accumulated other comprehensive loss Accumulated Other Comprehensive Income (Loss), Net of Tax Country Region Country Region Retirement Plan Sponsor Location [Domain] Retirement Plan Sponsor Location [Domain] Health Solutions Health Solutions [Member] Health Solutions Litigation Case [Axis] Litigation Case [Axis] NFP Intermediate Holdings A Corp. NFP Intermediate Holdings A Corp. [Member] NFP Intermediate Holdings A Corp. Segments [Domain] Segments [Domain] Damages sought Loss Contingency, Damages Sought, Value Income Statement Location [Axis] Statement of Income Location, Balance [Axis] Line of credit facility, available credit Line of Credit Facility, Remaining Borrowing Capacity Aggregate Pension Adjustments Service Cost Aggregate Pension Adjustments Service Cost [Member] Fair Value Hierarchy and NAV [Domain] Fair Value Hierarchy and NAV [Domain] Total Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), Reclassification, after Tax Balance Sheet Location [Domain] Statement of Financial Position Location, Balance [Domain] Finite-Lived Intangible Assets by Major Class [Axis] Finite-Lived Intangible Assets by Major Class [Axis] Guarantees of Aon plc’s 4.450% Senior Notes due 2043 Guarantees Of Aon Plc's 4.450% Senior Notes Due 2043 [Member] Guarantees Of Aon Plc's 4.450% Senior Notes Due 2043 [Member] Fatal Plain Crash In November 2016 Fatal Plain Crash In November 2016 [Member] Fatal Plain Crash In November 2016 Change in Fair Value of Financial Instruments AOCI, Accumulated Gain (Loss), Debt Securities, Available-for-Sale, Parent [Member] Company Selected Measure Name Company Selected Measure Name Fair Value Measurement [Domain] Fair Value Measurement [Domain] Senior notes Senior Notes [Member] Change in Capitalized Contract Costs Change In Capitalized Contract Costs [Roll Forward] Change In Capitalized Contract Costs [Roll Forward] Debt Debt Disclosure [Text Block] Aggregate Available Trading Arrangement, Securities Aggregate Available Amount Stock Appreciation Rights (SARs) Stock Appreciation Rights (SARs) [Member] Total liabilities assumed Business Combination, Recognized Liability Assumed, Liability All Executive Categories All Executive Categories [Member] Taxes receivable Income Taxes Receivable, Noncurrent Ordinary shares - $0.01 nominal value Authorized: 500.0 shares (issued: at March 31, 2026 - 213.6; at December 31, 2025 - 214.5) Common Stock, Value, Issued Goodwill [Roll Forward] Goodwill [Roll Forward] Restructuring Plan [Domain] Restructuring Plan [Domain] Short-term investments Short-Term Investments Claims, Lawsuits, and Other Contingencies Commitments and Contingencies Disclosure [Text Block] Total assets acquired Business Combination, Recognized Asset Acquired, Assets Acquired Including Goodwill Business Combination, Recognized Asset Acquired, Assets Acquired Including Goodwill Weighted average ordinary shares outstanding - diluted (in shares) Diluted weighted average ordinary shares outstanding (in shares) Weighted Average Number of Shares Outstanding, Diluted Non-GAAP Measure Description Non-GAAP Measure Description [Text Block] Human Capital Human Capital Human Capital Segment [Member] Human Capital Segment Derivative [Table] Derivative [Table] Business Combination [Axis] Business Combination [Axis] Entity Small Business Entity Small Business Percentage of capital acquired Business Combination, Voting Equity Interest Acquired, Percentage Income Tax Disclosure [Abstract] Income Tax Disclosure [Abstract] Net loss related to redeemable noncontrolling interest Net Income (Loss) Attributable to Redeemable Noncontrolling Interest Non- redeemable Non- controlling Interests Noncontrolling Interest [Member] Document Transition Report Document Transition Report Commercial paper issuances, net of repayments Proceeds from (Repayments of) Commercial Paper Underlying Securities Award Underlying Securities Amount Equity Component [Domain] Equity Component [Domain] Redeemable and nonredeemable noncontrolling interests, and other financing activities Proceeds From (Payments For) Noncontrolling Interests And Other Financing Activities Proceeds From (Payments For) Noncontrolling Interests And Other Financing Activities Document Period End Date Document Period End Date PEO Actually Paid Compensation Amount PEO Actually Paid Compensation Amount Income Taxes Income Tax Disclosure [Text Block] Guarantees of Aon Corporation and Aon Global Holdings plc’s 2.600% Senior Notes due 2031 Guarantees Of Aon Plc’s 2.600% Senior Notes Due 2031 [Member] Guarantees Of Aon Plc’s 2.60% Senior Notes Due 2031 Class A Ordinary Shares $0.01 nominal value Common Class A [Member] U.K. U.K. UNITED KINGDOM Awards Close in Time to MNPI Disclosures, Table Awards Close in Time to MNPI Disclosures [Table Text Block] Revenue from Contract with Customer [Abstract] Revenue from Contract with Customer [Abstract] Hedging Designation [Axis] Hedging Designation [Axis] Total equity Beginning balance Ending balance Equity, Including Portion Attributable to Noncontrolling Interest Average price per share (in dollars per share) Shares Acquired, Average Cost Per Share Goodwill Disposal Group, Including Discontinued Operation, Goodwill Document Type Document Type Significant Unobservable Inputs (Level 3) Fair Value, Inputs, Level 3 [Member] Name Outstanding Recovery, Individual Name Loss Contingencies [Table] Loss Contingencies [Table] Postretirement benefit obligation Net postretirement benefit obligation Other Comprehensive (Income) Loss, Defined Benefit Plan, after Reclassification Adjustment, after Tax Product and Service [Axis] Product and Service [Axis] Derivative Contract [Domain] Derivative Contract [Domain] Domestic Plan Domestic Plan [Member] Proceeds from issuance of shares Proceeds from Issuance of Common Stock Total revenue Total revenue Revenue from Contract with Customer, Excluding Assessed Tax Litigation Status [Domain] Litigation Status [Domain] All Individuals All Individuals [Member] Long-term Debt, Type [Domain] Long-Term Debt, Type [Domain] Commercial Risk Solutions Commercial Risk Solutions [Member] Commercial Risk Solutions Fair Value Disclosures [Abstract] Fair Value Disclosures [Abstract] Receivables, net Increase (Decrease) in Receivables Capital expenditures Payments to Acquire Property, Plant, and Equipment Name Forgone Recovery, Individual Name 8.205% Senior Notes due January 2027 8.205% Senior Notes Due January 2027 [Member] 8.205% Senior Notes Due January 2027 Total current assets Assets, Current Statistical Measurement [Axis] Statistical Measurement [Axis] Year-over-Year Change in Fair Value of Equity Awards Granted in Prior Years That are Outstanding and Unvested Year-over-Year Change in Fair Value of Equity Awards Granted in Prior Years That are Outstanding and Unvested [Member] Disposal Group Classification [Axis] Disposal Group Classification [Axis] Share repurchase authorization amount Share Repurchase Program, Authorized, Amount Reconciliation of cash and cash equivalents and funds held on behalf of clients: Cash, Cash Equivalent, Restricted Cash, and Restricted Cash Equivalent, Continuing Operation [Abstract] 2.875% Senior Notes Due May 2026 2.875% Senior Notes Due May 2026 [Member] 2.875% Senior Notes Due May 2026 Aggregate Erroneous Compensation Amount Aggregate Erroneous Compensation Amount Foreign currency translation and other Goodwill, Foreign Currency Translation, Gain (Loss) Disposal Group Name [Axis] Disposal Group Name [Axis] Cash paid for employee taxes on withholding shares Payment, Tax Withholding, Share-Based Payment Arrangement Net sale (purchases) of short-term investments - non fiduciary Payments for (Proceeds from) Marketable Securities The cash inflow or outflow from sales or purchases of marketable securities. Peer Group Issuers, Footnote Peer Group Issuers, Footnote [Text Block] Term of derivative contract Derivative, Term of Contract Restructuring plan, period Restructuring And Related Cost, Period Restructuring And Related Cost, Period Schedule of Notional and Fair Values of Derivative Instruments Schedule of Derivative Instruments [Table Text Block] Guarantees of Aon Corporation and Aon Global Holdings plc’s 2.900% Senior Notes due 2051 Guarantees Of Aon Plc's 2.900% Senior Notes Due 2051 [Member] Guarantees Of Aon Plc's 2.900% Senior Notes Due 2051 Entity Information [Line Items] Entity Information [Line Items] Erroneous Compensation Analysis Erroneous Compensation Analysis [Text Block] Schedule of Finite-Lived Intangible Assets by Major Class [Table] Intangible Asset, Finite-Lived [Table] Current liabilities Liabilities, Current [Abstract] Total other comprehensive income (loss) attributable to Aon shareholders Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent Geographical [Axis] Geographical [Axis] Schedule of Derivative Gains (Losses) Derivative Instruments, Gain (Loss) [Table Text Block] Other assets and liabilities Increase (Decrease) in Other Operating Assets and Liabilities, Net Rule 10b5-1 Arrangement Terminated Rule 10b5-1 Arrangement Terminated [Flag] Quoted Prices in Active Markets for Identical Assets (Level 1) Fair Value, Inputs, Level 1 [Member] Foreign currency remeasurement Gain (Loss), Foreign Currency Transaction, before Tax Asia Pacific Asia Pacific [Member] Diluted net income per share attributable to Aon shareholders (in dollars per share) Earnings Per Share, Diluted Erroneously Awarded Compensation Recovery Erroneously Awarded Compensation Recovery [Table] Receivables, net Accounts Receivable, after Allowance for Credit Loss, Current Title of 12(b) Security Title of 12(b) Security Griffiths & armour Griffiths & Armour [Member] Griffiths & Armour Disposal Groups, Including Discontinued Operations [Table] Disposal Groups, Including Discontinued Operations [Table] Number of plaintiffs Loss Contingency, Number of Plaintiffs Expected future employer cash contribution Defined Benefit Plan, Expected Future Employer Contributions, Remainder of Fiscal Year Amortization Capitalized Contract Cost, Amortization Technology and other Marketing Technology and Other [Member] Represents finite-lived intangible assets related to marketing and technology. Operating funds required to be held in U.K. Short-Term Investments, Operating Funds Required To Be Held Short-Term Investments, Operating Funds Required To Be Held Restructuring Plan [Axis] Restructuring Plan [Axis] Schedule of Commercial Paper Outstanding Schedule Of Commercial Paper Outstanding [Table Text Block] Schedule Of Commercial Paper Outstanding Consolidation Items [Domain] Consolidation Items [Domain] Funds held on behalf of clients Funds Held for Clients Shares repurchased Total cost of shares purchased Repurchase costs recorded to retained earnings (accumulated deficit) Stock Repurchased and Retired During Period, Value Guarantees of Aon plc’s 4.750% Senior Notes due 2045 Guarantees Of Aon Plc's 4.750% Senior Notes Due 2045 [Member] Guarantees Of Aon Plc's 4.750% Senior Notes Due 2045 [Member] Short-term Debt, Type [Axis] Short-Term Debt, Type [Axis] Intangible assets, net Disposal Group, Including Discontinued Operation, Intangible Assets Number of defendants Loss Contingency, Number of Defendants Income taxes paid, net of refunds Income Taxes Paid, Net 2028 Finite-Lived Intangible Asset, Expected Amortization, Year Two Award Timing Disclosures [Line Items] Service cost Defined Benefit Plan, Service Cost Foreign currency translation and other Restructuring Reserve, Foreign Currency Translation Gain (Loss) Change in fair value of financial instruments Net change in fair value of financial instruments OCI, Debt Securities, Available-for-Sale, Unrealized Holding Gain (Loss), before Adjustment, after Tax Other comprehensive income (loss) before reclassifications, net Other Comprehensive Income (Loss), before Reclassifications, Net of Tax Shareholders’ Equity Equity [Text Block] Dividends paid to nonredeemable noncontrolling interests on subsidiary common stock Noncontrolling Interest, Decrease from Distributions to Noncontrolling Interest Holders Schedule of Other Current Liabilities Other Current Liabilities [Table Text Block] Tradenames Trade Names [Member] Net income attributable to Aon shareholders Net Income (Loss) Attributable to Parent Eliminations Intersegment Eliminations [Member] Expiration Date Trading Arrangement Expiration Date Pending Litigation Pending Litigation [Member] 2031 Finite-Lived Intangible Asset, Expected Amortization, Year Five Other Other Accrued Liabilities, Current Equity Equity, Including Portion Attributable to Noncontrolling Interest [Abstract] Fixed assets, net Property, Plant and Equipment, Net Segment Reporting Information [Line Items] Segment Reporting Information [Line Items] Accelerating Aon United Program expenses Charges Total Restructuring Charges Adoption Date Trading Arrangement Adoption Date Compensation Actually Paid vs. Net Income Compensation Actually Paid vs. Net Income [Text Block] Schedule of Restructuring and Related Costs [Table] Restructuring Cost [Table] Entity Current Reporting Status Entity Current Reporting Status Credit facility expiring october 2028 Credit Facility Expiring October 2028 [Member] Credit Facility Expiring October 2028 Derivative [Line Items] Derivative [Line Items] Awards Close in Time to MNPI Disclosures Awards Close in Time to MNPI Disclosures [Table] Operating income Operating Income (Loss) Capital Unit [Line Items] Capital Unit [Line Items] Line of Credit Line of Credit [Member] Retained earnings (Accumulated deficit) Retained Earnings (Accumulated Deficit) Increase (decrease) in fiduciary liabilities, net of fiduciary receivables Increase In Fiduciary Liabilities, Net Of Fiduciary Receivables Increase In Fiduciary Liabilities, Net Of Fiduciary Receivables Statement of Financial Position [Abstract] Statement of Financial Position [Abstract] Year-end Fair Value of Equity Awards Granted in Covered Year that are Outstanding and Unvested Year-end Fair Value of Equity Awards Granted in Covered Year that are Outstanding and Unvested [Member] Executive Category: Executive Category [Axis] Capitalized Cost To Fulfill Customer Contracts Capitalized Cost To Fulfill Customer Contracts [Member] Capitalized Cost To Fulfill Customer Contracts [Member] Guarantees of Aon Corporation and Aon Global Holdings plc’s 2.850% Senior Notes due 2027 Guarantees of Aon Corporation and Aon Global Holdings plc’s 2.850% Senior Notes due 2027 [Member] Guarantees of Aon Corporation and Aon Global Holdings plc’s 2.850% Senior Notes due 2027 Current Fiscal Year End Date Current Fiscal Year End Date Class of Stock [Axis] Class of Stock [Axis] Guarantees of Aon Corporation and Aon Global Holdings plc’s 5.350% Senior Notes due 2033 Guarantees Of Aon Plc’s 5.350% Senior Notes Due 2033 [Member] Guarantees Of Aon Plc’s 5.350% Senior Notes Due 2033 Ireland IRELAND Subsequent Event Type [Domain] Subsequent Event Type [Domain] Finite-Lived Intangible Assets, Major Class Name [Domain] Finite-Lived Intangible Assets, Major Class Name [Domain] Aggregate Grant Date Fair Value of Equity Award Amounts Reported in Summary Compensation Table Aggregate Grant Date Fair Value of Equity Award Amounts Reported in Summary Compensation Table [Member] Statement [Table] Statement [Table] Other income (expense) Total Other income (expense) Other Nonoperating Income (Expense) Derivatives Derivative Liability Schedule of Total Acquisitions Business Combination [Table Text Block] Amortization and impairment of intangible assets Amortization And Impairment Of Intangible Assets Amortization And Impairment Of Intangible Assets Adjustments to reconcile net income to cash provided by operating activities: Adjustment to Reconcile Net Income to Cash Provided by (Used in) Operating Activity [Abstract] Cash flows from financing activities Cash Provided by (Used in) Financing Activity, Including Discontinued Operation [Abstract] 5.125% Senior Notes Due March 2027 5.125% Senior Notes Due March 2027 [Member] 5.125% Senior Notes Due March 2027 Equity Awards Adjustments, Excluding Value Reported in Compensation Table Equity Awards Adjustments, Excluding Value Reported in the Compensation Table [Member] Net assets acquired Business Combination, Recognized Asset Acquired to Liability Assumed, Excess (Less), and Goodwill Schedule of Assets and Liabilities That are Measured at Fair Value on a Recurring Basis Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis [Table Text Block] Basis of Presentation Organization, Consolidation and Presentation of Financial Statements Disclosure [Text Block] Money market funds Basis Money Market Funds and Highly Liquid Securities, Fair Value Disclosure Represents the fair value of money market funds and other highly liquid securities. Antidilutive securities excluded from computation of earnings per share (in shares) Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount All Adjustments to Compensation All Adjustments to Compensation [Member] Accounts payable and accrued liabilities Accounts Payable and Accrued Liabilities, Current Amendment Flag Amendment Flag Other Financial Data [Abstract] Other Financial Data [Abstract] Other Financial Data [Abstract] Termination Date Trading Arrangement Termination Date Cash used for financing activities Cash Provided by (Used in) Financing Activity, Including Discontinued Operation Guarantees of Aon North America, Inc.’s 5.150% Senior Notes due 2029 Guarantees Of Aon North America, Inc.’s 5.150% Senior Notes Due 2029 [Member] Guarantees Of Aon North America, Inc.’s 5.150% Senior Notes Due 2029 Insider Trading Policies and Procedures Adopted Insider Trading Policies and Procedures Adopted [Flag] Measure: Measure [Axis] Thereafter Finite-Lived Intangible Asset, Expected Amortization, after Year Five Weighted average ordinary shares outstanding - basic (in shares) Basic weighted average ordinary shares outstanding (in shares) Weighted Average Number of Shares Outstanding, Basic Share repurchase, remaining authorized repurchase amount Share Repurchase Program, Remaining Authorized, Amount Guarantees of Aon Corporation and Aon Global Holdings plc’s 5.000% Senior Notes due 2032 Guarantees Of Aon Plc’s 5.000% Senior Notes Due 2032 [Member] Guarantees Of Aon Plc’s 5.000% Senior Notes Due 2032 [Member] Disposal Group Classification [Domain] Disposal Group Classification [Domain] Technology and other Technology And Other [Member] Technology And Other Capitalized Contract Cost [Line Items] Capitalized Contract Cost [Line Items] Total Business Combination, Number of Businesses Acquired Segment Reporting [Abstract] Segment Reporting [Abstract] Impairment Capitalized Contract Cost, Impairment Loss Pay vs Performance Disclosure, Table Pay vs Performance [Table Text Block] Debt Disclosure [Abstract] Debt Disclosure [Abstract] Forgone Recovery due to Violation of Home Country Law, Amount Forgone Recovery due to Violation of Home Country Law, Amount Ordinary Shares and Additional Paid-in Capital Common Stock Including Additional Paid in Capital [Member] Entity Tax Identification Number Entity Tax Identification Number Expenses Costs and Expenses [Abstract] Tax expense Reclassification from AOCI, Current Period, Tax Reinsurance Solutions Reinsurance Solutions [Member] Reinsurance Solutions Guarantees of Aon plc’s 4.250% Senior Notes due 2042 Guarantees Of Aon Plc's 4.250% Senior Notes Due 2042 [Member] Guarantees Of Aon Plc's 4.250% Senior Notes Due 2042 [Member] Restructuring and Related Activities [Abstract] Restructuring and Related Activities [Abstract] Forgone Recovery due to Expense of Enforcement, Amount Forgone Recovery due to Expense of Enforcement, Amount Ordinary shares, nominal value (in dollars per share) Common Stock, Par or Stated Value Per Share Schedule of Components of Weighted Average Number of Shares Outstanding Schedule of Weighted Average Number of Shares [Table Text Block] Ordinary shares, issued shares (in shares) Beginning balance (in shares) Ending balance (in shares) Common Stock, Shares, Issued Taxes receivable Income Taxes Receivable, Current Goodwill and Other Intangible Assets Goodwill and Intangible Assets Disclosure [Text Block] Guarantees of Aon plc’s 4.600% Senior Notes due 2044 Guarantees Of Aon Plc's 4.600% Senior Notes Due 2044 [Member] Guarantees Of Aon Plc's 4.600% Senior Notes Due 2044 [Member] Use of Estimates Use of Estimates, Policy [Policy Text Block] Premises Occupancy, Net Schedule of Changes in the Net Carrying Amount of Goodwill by Operating Segment Schedule of Goodwill [Table Text Block] Interest expense Interest Expense, Nonoperating Trading Arrangement: Trading Arrangement [Axis] Current income taxes Increase (Decrease) in Income Taxes Payable Total Shareholder Return Amount Total Shareholder Return Amount Schedule of Other Non-current Assets Schedule of Other Assets, Noncurrent [Table Text Block] Legal, Guarantees and Indemnifications Loss Contingencies [Line Items] Foreign currency translation adjustments Net foreign currency translation adjustments Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Adjustment, Net of Tax Insider Trading Arrangements [Line Items] Corporate Segment Reporting, Reconciling Item, Corporate Nonsegment [Member] Security Exchange Name Security Exchange Name Interest income Investment Income, Interest and Dividend Total liabilities Liabilities Non-cash charges Restructuring Reserve, Settled (Reversed) Without Cash Restructuring Reserve, Settled (Reversed) Without Cash Amounts reclassified from accumulated other comprehensive income Other Comprehensive Income (Loss), Net of Tax, Period Change [Abstract] Investment income Investment Income, Net Maximum borrowing capacity Line of Credit Facility, Maximum Borrowing Capacity Pension Adjustments Prior Service Cost Pension Adjustments Prior Service Cost [Member] Guarantees of Aon Corporation and Aon Global Holdings plc’s 3.900% Senior Notes due 2052 Guarantees of Aon Corporation and Aon Global Holdings plc’s 3.900% Senior Notes due 2052 [Member] Guarantees of Aon Corporation and Aon Global Holdings plc’s 3.900% Senior Notes due 2052 Prepaid expenses Prepaid Expense, Current Material Terms of Trading Arrangement Material Terms of Trading Arrangement [Text Block] Other current liabilities Total Other Liabilities, Current Loss on disposition of business Loss On Disposition Of Business Loss On Disposition Of Business Statement [Line Items] Statement [Line Items] Equity, Capital Unit or Share [Table] Equity, Capital Unit or Share [Table] Consolidation Items [Axis] Consolidation Items [Axis] Schedule of Restructuring Liabilities for the Program Schedule of Restructuring Reserve by Type of Cost [Table Text Block] Rule 10b5-1 Arrangement Adopted Rule 10b5-1 Arrangement Adopted [Flag] Cash and cash equivalents Cash and cash equivalents Cash and Cash Equivalent Compensation and benefits Compensation And Benefits [Member] Compensation And Benefits Net income Net Income (Loss), Including Portion Attributable to Nonredeemable Noncontrolling Interest Entity Incorporation, State or Country Code Entity Incorporation, State or Country Code Non-NEOs Non-NEOs [Member] Net increase (decrease) in cash and cash equivalents and funds held on behalf of clients Cash, Cash Equivalent, Restricted Cash, and Restricted Cash Equivalent, Period Increase (Decrease), Including Exchange Rate Effect and Discontinued Operation