0000001 - Document - Cover link:presentationLink link:calculationLink link:definitionLink 9952151 - Statement - Condensed Consolidated Statements of Income (Unaudited) link:presentationLink link:calculationLink link:definitionLink 9952152 - Statement - Condensed Consolidated Statements of Comprehensive Income (Unaudited) link:presentationLink link:calculationLink link:definitionLink 9952153 - Statement - Condensed Consolidated Statements of Financial Position link:presentationLink link:calculationLink link:definitionLink 9952154 - Statement - Condensed Consolidated Statements of Financial Position (Parenthetical) link:presentationLink link:calculationLink link:definitionLink 9952155 - Statement - Condensed Consolidated Statements of Shareholders’ Equity (Unaudited) link:presentationLink link:calculationLink link:definitionLink 9952156 - Statement - Condensed Consolidated Statements of Shareholders’ Equity (Unaudited) (Parenthetical) link:presentationLink link:calculationLink link:definitionLink 9952157 - Statement - Condensed Consolidated Statements of Cash Flows (Unaudited) link:presentationLink link:calculationLink link:definitionLink 9952158 - Disclosure - Basis of Presentation link:presentationLink link:calculationLink link:definitionLink 9952159 - Disclosure - Accounting Principles and Practices link:presentationLink link:calculationLink link:definitionLink 9952160 - Disclosure - Revenue from Contracts with Customers link:presentationLink link:calculationLink link:definitionLink 9952161 - Disclosure - Accelerating Aon United Program link:presentationLink link:calculationLink link:definitionLink 9952162 - Disclosure - Cash and Cash Equivalents and Short-Term Investments link:presentationLink link:calculationLink link:definitionLink 9952163 - Disclosure - Other Financial Data link:presentationLink link:calculationLink link:definitionLink 9952164 - Disclosure - Acquisitions and Dispositions of Businesses link:presentationLink link:calculationLink link:definitionLink 9952165 - Disclosure - Goodwill and Other Intangible Assets link:presentationLink link:calculationLink link:definitionLink 9952166 - Disclosure - Debt link:presentationLink link:calculationLink link:definitionLink 9952167 - Disclosure - Income Taxes link:presentationLink link:calculationLink link:definitionLink 9952168 - Disclosure - Shareholders' Equity link:presentationLink link:calculationLink link:definitionLink 9952169 - Disclosure - Employee Benefits link:presentationLink link:calculationLink link:definitionLink 9952170 - Disclosure - Derivatives and Hedging link:presentationLink link:calculationLink link:definitionLink 9952171 - Disclosure - Fair Value Measurements and Financial Instruments link:presentationLink link:calculationLink link:definitionLink 9952172 - Disclosure - Claims, Lawsuits, and Other Contingencies link:presentationLink link:calculationLink link:definitionLink 9952173 - Disclosure - Segment Information link:presentationLink link:calculationLink link:definitionLink 9955511 - Disclosure - Accounting Principles and Practices (Policies) link:presentationLink link:calculationLink link:definitionLink 9955512 - Disclosure - Revenue from Contracts with Customers (Tables) link:presentationLink link:calculationLink link:definitionLink 9955513 - Disclosure - Accelerating Aon United Program (Tables) link:presentationLink link:calculationLink link:definitionLink 9955514 - Disclosure - Other Financial Data (Tables) link:presentationLink link:calculationLink link:definitionLink 9955515 - Disclosure - Acquisitions and Dispositions of Businesses (Tables) link:presentationLink link:calculationLink link:definitionLink 9955516 - Disclosure - Goodwill and Other Intangible Assets (Tables) link:presentationLink link:calculationLink link:definitionLink 9955517 - Disclosure - Debt (Tables) link:presentationLink link:calculationLink link:definitionLink 9955518 - Disclosure - Shareholders' Equity (Tables) link:presentationLink link:calculationLink link:definitionLink 9955519 - Disclosure - Employee Benefits (Tables) link:presentationLink link:calculationLink link:definitionLink 9955520 - Disclosure - Derivatives and Hedging (Tables) link:presentationLink link:calculationLink link:definitionLink 9955521 - Disclosure - Fair Value Measurements and Financial Instruments (Tables) link:presentationLink link:calculationLink link:definitionLink 9955522 - Disclosure - Segment Information (Tables) link:presentationLink link:calculationLink link:definitionLink 9955523 - Disclosure - Revenue from Contracts with Customers - Schedule of Disaggregation of Revenue (Details) link:presentationLink link:calculationLink link:definitionLink 9955524 - Disclosure - Revenue from Contracts with Customers - Schedule of Contract Assets Rollforward (Details) link:presentationLink link:calculationLink link:definitionLink 9955525 - Disclosure - Accelerating Aon United Program - Narrative (Details) link:presentationLink link:calculationLink link:definitionLink 9955526 - Disclosure - Accelerating Aon United Program - Schedule of Program Costs Incurred (Details) link:presentationLink link:calculationLink link:definitionLink 9955527 - Disclosure - Accelerating Aon United Program - Schedule of Changes in the Company’s Liabilities for the Program (Details) link:presentationLink link:calculationLink link:definitionLink 9955528 - Disclosure - Cash and Cash Equivalents and Short-Term Investments (Details) link:presentationLink link:calculationLink link:definitionLink 9955529 - Disclosure - Other Financial Data - Schedule of Other Income (Expense) (Details) link:presentationLink link:calculationLink link:definitionLink 9955530 - Disclosure - Other Financial Data - Schedule of Allowance for Doubtful Accounts (Details) link:presentationLink link:calculationLink link:definitionLink 9955531 - Disclosure - Other Financial Data - Schedule of Other Current Assets (Details) link:presentationLink link:calculationLink link:definitionLink 9955532 - Disclosure - Other Financial Data - Schedule of Other Non-current Assets (Details) link:presentationLink link:calculationLink link:definitionLink 9955533 - Disclosure - Other Financial Data - 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Disclosure - Goodwill and Other Intangible Assets - Schedule of Other Intangible Assets by Asset Class (Details) link:presentationLink link:calculationLink link:definitionLink 9955540 - Disclosure - Goodwill and Other Intangible Assets - Schedule of Estimated Future Amortization Expense on Intangible Assets (Details) link:presentationLink link:calculationLink link:definitionLink 9955541 - Disclosure - Debt - Narrative (Details) link:presentationLink link:calculationLink link:definitionLink 9955542 - Disclosure - Debt - Schedule of Commercial Paper Outstanding (Details) link:presentationLink link:calculationLink link:definitionLink 9955543 - Disclosure - Income Taxes (Details) link:presentationLink link:calculationLink link:definitionLink 9955544 - Disclosure - Shareholders' Equity - Narrative (Details) link:presentationLink link:calculationLink link:definitionLink 9955545 - Disclosure - Shareholders' Equity - Schedule of Share Repurchases Activity (Details) link:presentationLink link:calculationLink link:definitionLink 9955546 - Disclosure - Shareholders' Equity - Schedule of Components of Weighted Average Ordinary Shares Outstanding (Details) link:presentationLink link:calculationLink link:definitionLink 9955547 - Disclosure - Shareholders' Equity - Schedule of Components of Accumulated Other Comprehensive Loss (Details) link:presentationLink link:calculationLink link:definitionLink 9955548 - Disclosure - Employee Benefits - Schedule of Components of Net Periodic (Benefit) Cost (Details) link:presentationLink link:calculationLink link:definitionLink 9955549 - Disclosure - Employee Benefits - Narrative (Details) link:presentationLink link:calculationLink link:definitionLink 9955550 - Disclosure - Employee Benefits - Schedule of Employer Contributions (Details) link:presentationLink link:calculationLink link:definitionLink 9955551 - Disclosure - Derivatives and Hedging - Narrative (Details) link:presentationLink link:calculationLink link:definitionLink 9955552 - Disclosure - Derivatives and Hedging - Schedule of Notional and Fair Values of Derivative Instruments (Details) link:presentationLink link:calculationLink link:definitionLink 9955552 - Disclosure - Derivatives and Hedging - Schedule of Notional and Fair Values of Derivative Instruments (Details) link:presentationLink link:calculationLink link:definitionLink 9955553 - Disclosure - Derivatives and Hedging - Schedule of Derivative Gains (Losses) Recognized in the Consolidated Financial Statements (Details) link:presentationLink link:calculationLink link:definitionLink 9955553 - Disclosure - Derivatives and Hedging - Schedule of Derivative Gains (Losses) Recognized in the Consolidated Financial Statements (Details) link:presentationLink link:calculationLink link:definitionLink 9955554 - Disclosure - Fair Value Measurements and Financial Instruments - Schedule of Assets and Liabilities that are Measured at Fair Value on a Recurring Basis (Details) link:presentationLink link:calculationLink link:definitionLink 9955555 - Disclosure - Fair Value Measurements and Financial Instruments - Schedule of Financial Instruments where the Carrying Amounts and Fair Values Differ (Details) link:presentationLink link:calculationLink link:definitionLink 9955556 - Disclosure - Claims, Lawsuits, and Other Contingencies - Legal Narrative (Details) link:presentationLink link:calculationLink link:definitionLink 9955557 - Disclosure - Claims, Lawsuits, and Other Contingencies - Letters of Credit Narrative (Details) link:presentationLink link:calculationLink link:definitionLink 9955558 - Disclosure - Claims, Lawsuits, and Other Contingencies - Premium Payments Narrative (Details) link:presentationLink link:calculationLink link:definitionLink 9955559 - Disclosure - Segment Information - Narrative (Details) link:presentationLink link:calculationLink link:definitionLink 9955560 - Disclosure - Segment Information - Schedule of Reportable Operating Segments, Consolidated Revenue and Segment Operating Income (Details) link:presentationLink link:calculationLink link:definitionLink