XML 56 R111.htm IDEA: XBRL DOCUMENT
v2.4.1.9

Derivatives and Hedging - Schedule of amounts of derivative gains (losses) recognized in the Consolidated Financial Statements (Details) (Designated as Hedging Instrument [Member], USD $) In Millions, unless otherwise specified | 12 Months Ended
--- | ---
Dec. 31, 2014 | Dec. 31, 2013 | Dec. 31, 2012
Cash Flow Hedging [Member] |  |  |
Derivative [Line Items] |  |  |
Gain (loss) recognized in accumulated other comprehensive income | $ (2)us-gaap_DerivativeInstrumentsGainLossRecognizedInOtherComprehensiveIncomeEffectivePortionNet / us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis = us-gaap_CashFlowHedgingMember / us-gaap_HedgingDesignationAxis = us-gaap_DesignatedAsHedgingInstrumentMember | $ (2)us-gaap_DerivativeInstrumentsGainLossRecognizedInOtherComprehensiveIncomeEffectivePortionNet / us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis = us-gaap_CashFlowHedgingMember / us-gaap_HedgingDesignationAxis = us-gaap_DesignatedAsHedgingInstrumentMember | $ (21)us-gaap_DerivativeInstrumentsGainLossRecognizedInOtherComprehensiveIncomeEffectivePortionNet / us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis = us-gaap_CashFlowHedgingMember / us-gaap_HedgingDesignationAxis = us-gaap_DesignatedAsHedgingInstrumentMember
Gain (loss) reclassified from accumulated other comprehensive loss into income (effective portion) | (15)us-gaap_DerivativeInstrumentsGainLossReclassifiedFromAccumulatedOCIIntoIncomeEffectivePortionNet / us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis = us-gaap_CashFlowHedgingMember / us-gaap_HedgingDesignationAxis = us-gaap_DesignatedAsHedgingInstrumentMember | (11)us-gaap_DerivativeInstrumentsGainLossReclassifiedFromAccumulatedOCIIntoIncomeEffectivePortionNet / us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis = us-gaap_CashFlowHedgingMember / us-gaap_HedgingDesignationAxis = us-gaap_DesignatedAsHedgingInstrumentMember | (35)us-gaap_DerivativeInstrumentsGainLossReclassifiedFromAccumulatedOCIIntoIncomeEffectivePortionNet / us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis = us-gaap_CashFlowHedgingMember / us-gaap_HedgingDesignationAxis = us-gaap_DesignatedAsHedgingInstrumentMember
Cash Flow Hedging [Member] | Compensation and Benefits [Member] |  |  |
Derivative [Line Items] |  |  |
Gain (loss) recognized in accumulated other comprehensive income | 11 us-gaap_DerivativeInstrumentsGainLossRecognizedInOtherComprehensiveIncomeEffectivePortionNet / us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis = us-gaap_CashFlowHedgingMember / us-gaap_HedgingDesignationAxis = us-gaap_DesignatedAsHedgingInstrumentMember / us-gaap_IncomeStatementLocationAxis = aon_CompensationandBenefitsMember | (17)us-gaap_DerivativeInstrumentsGainLossRecognizedInOtherComprehensiveIncomeEffectivePortionNet / us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis = us-gaap_CashFlowHedgingMember / us-gaap_HedgingDesignationAxis = us-gaap_DesignatedAsHedgingInstrumentMember / us-gaap_IncomeStatementLocationAxis = aon_CompensationandBenefitsMember | (8)us-gaap_DerivativeInstrumentsGainLossRecognizedInOtherComprehensiveIncomeEffectivePortionNet / us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis = us-gaap_CashFlowHedgingMember / us-gaap_HedgingDesignationAxis = us-gaap_DesignatedAsHedgingInstrumentMember / us-gaap_IncomeStatementLocationAxis = aon_CompensationandBenefitsMember
Gain (loss) reclassified from accumulated other comprehensive loss into income (effective portion) | (5)us-gaap_DerivativeInstrumentsGainLossReclassifiedFromAccumulatedOCIIntoIncomeEffectivePortionNet / us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis = us-gaap_CashFlowHedgingMember / us-gaap_HedgingDesignationAxis = us-gaap_DesignatedAsHedgingInstrumentMember / us-gaap_IncomeStatementLocationAxis = aon_CompensationandBenefitsMember | (12)us-gaap_DerivativeInstrumentsGainLossReclassifiedFromAccumulatedOCIIntoIncomeEffectivePortionNet / us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis = us-gaap_CashFlowHedgingMember / us-gaap_HedgingDesignationAxis = us-gaap_DesignatedAsHedgingInstrumentMember / us-gaap_IncomeStatementLocationAxis = aon_CompensationandBenefitsMember | (9)us-gaap_DerivativeInstrumentsGainLossReclassifiedFromAccumulatedOCIIntoIncomeEffectivePortionNet / us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis = us-gaap_CashFlowHedgingMember / us-gaap_HedgingDesignationAxis = us-gaap_DesignatedAsHedgingInstrumentMember / us-gaap_IncomeStatementLocationAxis = aon_CompensationandBenefitsMember
Cash Flow Hedging [Member] | Other General Expenses [Member] |  |  |
Derivative [Line Items] |  |  |
Gain (loss) recognized in accumulated other comprehensive income | (3)us-gaap_DerivativeInstrumentsGainLossRecognizedInOtherComprehensiveIncomeEffectivePortionNet / us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis = us-gaap_CashFlowHedgingMember / us-gaap_HedgingDesignationAxis = us-gaap_DesignatedAsHedgingInstrumentMember / us-gaap_IncomeStatementLocationAxis = aon_OtherGeneralExpensesMember | 0 us-gaap_DerivativeInstrumentsGainLossRecognizedInOtherComprehensiveIncomeEffectivePortionNet / us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis = us-gaap_CashFlowHedgingMember / us-gaap_HedgingDesignationAxis = us-gaap_DesignatedAsHedgingInstrumentMember / us-gaap_IncomeStatementLocationAxis = aon_OtherGeneralExpensesMember | (19)us-gaap_DerivativeInstrumentsGainLossRecognizedInOtherComprehensiveIncomeEffectivePortionNet / us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis = us-gaap_CashFlowHedgingMember / us-gaap_HedgingDesignationAxis = us-gaap_DesignatedAsHedgingInstrumentMember / us-gaap_IncomeStatementLocationAxis = aon_OtherGeneralExpensesMember
Gain (loss) reclassified from accumulated other comprehensive loss into income (effective portion) | 3 us-gaap_DerivativeInstrumentsGainLossReclassifiedFromAccumulatedOCIIntoIncomeEffectivePortionNet / us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis = us-gaap_CashFlowHedgingMember / us-gaap_HedgingDesignationAxis = us-gaap_DesignatedAsHedgingInstrumentMember / us-gaap_IncomeStatementLocationAxis = aon_OtherGeneralExpensesMember | (9)us-gaap_DerivativeInstrumentsGainLossReclassifiedFromAccumulatedOCIIntoIncomeEffectivePortionNet / us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis = us-gaap_CashFlowHedgingMember / us-gaap_HedgingDesignationAxis = us-gaap_DesignatedAsHedgingInstrumentMember / us-gaap_IncomeStatementLocationAxis = aon_OtherGeneralExpensesMember | (16)us-gaap_DerivativeInstrumentsGainLossReclassifiedFromAccumulatedOCIIntoIncomeEffectivePortionNet / us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis = us-gaap_CashFlowHedgingMember / us-gaap_HedgingDesignationAxis = us-gaap_DesignatedAsHedgingInstrumentMember / us-gaap_IncomeStatementLocationAxis = aon_OtherGeneralExpensesMember
Cash Flow Hedging [Member] | Interest Expense [Member] |  |  |
Derivative [Line Items] |  |  |
Gain (loss) recognized in accumulated other comprehensive income | 0 us-gaap_DerivativeInstrumentsGainLossRecognizedInOtherComprehensiveIncomeEffectivePortionNet / us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis = us-gaap_CashFlowHedgingMember / us-gaap_HedgingDesignationAxis = us-gaap_DesignatedAsHedgingInstrumentMember / us-gaap_IncomeStatementLocationAxis = us-gaap_InterestExpenseMember | 2 us-gaap_DerivativeInstrumentsGainLossRecognizedInOtherComprehensiveIncomeEffectivePortionNet / us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis = us-gaap_CashFlowHedgingMember / us-gaap_HedgingDesignationAxis = us-gaap_DesignatedAsHedgingInstrumentMember / us-gaap_IncomeStatementLocationAxis = us-gaap_InterestExpenseMember | 0 us-gaap_DerivativeInstrumentsGainLossRecognizedInOtherComprehensiveIncomeEffectivePortionNet / us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis = us-gaap_CashFlowHedgingMember / us-gaap_HedgingDesignationAxis = us-gaap_DesignatedAsHedgingInstrumentMember / us-gaap_IncomeStatementLocationAxis = us-gaap_InterestExpenseMember
Gain (loss) reclassified from accumulated other comprehensive loss into income (effective portion) | (11)us-gaap_DerivativeInstrumentsGainLossReclassifiedFromAccumulatedOCIIntoIncomeEffectivePortionNet / us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis = us-gaap_CashFlowHedgingMember / us-gaap_HedgingDesignationAxis = us-gaap_DesignatedAsHedgingInstrumentMember / us-gaap_IncomeStatementLocationAxis = us-gaap_InterestExpenseMember | (4)us-gaap_DerivativeInstrumentsGainLossReclassifiedFromAccumulatedOCIIntoIncomeEffectivePortionNet / us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis = us-gaap_CashFlowHedgingMember / us-gaap_HedgingDesignationAxis = us-gaap_DesignatedAsHedgingInstrumentMember / us-gaap_IncomeStatementLocationAxis = us-gaap_InterestExpenseMember | (1)us-gaap_DerivativeInstrumentsGainLossReclassifiedFromAccumulatedOCIIntoIncomeEffectivePortionNet / us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis = us-gaap_CashFlowHedgingMember / us-gaap_HedgingDesignationAxis = us-gaap_DesignatedAsHedgingInstrumentMember / us-gaap_IncomeStatementLocationAxis = us-gaap_InterestExpenseMember
Cash Flow Hedging [Member] | Other Income [Member] |  |  |
Derivative [Line Items] |  |  |
Gain (loss) recognized in accumulated other comprehensive income | (10)us-gaap_DerivativeInstrumentsGainLossRecognizedInOtherComprehensiveIncomeEffectivePortionNet / us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis = us-gaap_CashFlowHedgingMember / us-gaap_HedgingDesignationAxis = us-gaap_DesignatedAsHedgingInstrumentMember / us-gaap_IncomeStatementLocationAxis = us-gaap_OtherIncomeMember | 13 us-gaap_DerivativeInstrumentsGainLossRecognizedInOtherComprehensiveIncomeEffectivePortionNet / us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis = us-gaap_CashFlowHedgingMember / us-gaap_HedgingDesignationAxis = us-gaap_DesignatedAsHedgingInstrumentMember / us-gaap_IncomeStatementLocationAxis = us-gaap_OtherIncomeMember | 6 us-gaap_DerivativeInstrumentsGainLossRecognizedInOtherComprehensiveIncomeEffectivePortionNet / us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis = us-gaap_CashFlowHedgingMember / us-gaap_HedgingDesignationAxis = us-gaap_DesignatedAsHedgingInstrumentMember / us-gaap_IncomeStatementLocationAxis = us-gaap_OtherIncomeMember
Gain (loss) reclassified from accumulated other comprehensive loss into income (effective portion) | (2)us-gaap_DerivativeInstrumentsGainLossReclassifiedFromAccumulatedOCIIntoIncomeEffectivePortionNet / us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis = us-gaap_CashFlowHedgingMember / us-gaap_HedgingDesignationAxis = us-gaap_DesignatedAsHedgingInstrumentMember / us-gaap_IncomeStatementLocationAxis = us-gaap_OtherIncomeMember | 14 us-gaap_DerivativeInstrumentsGainLossReclassifiedFromAccumulatedOCIIntoIncomeEffectivePortionNet / us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis = us-gaap_CashFlowHedgingMember / us-gaap_HedgingDesignationAxis = us-gaap_DesignatedAsHedgingInstrumentMember / us-gaap_IncomeStatementLocationAxis = us-gaap_OtherIncomeMember | (9)us-gaap_DerivativeInstrumentsGainLossReclassifiedFromAccumulatedOCIIntoIncomeEffectivePortionNet / us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis = us-gaap_CashFlowHedgingMember / us-gaap_HedgingDesignationAxis = us-gaap_DesignatedAsHedgingInstrumentMember / us-gaap_IncomeStatementLocationAxis = us-gaap_OtherIncomeMember
Cash Flow Hedging [Member] | Interest rate contracts [Member] |  |  |
Derivative [Line Items] |  |  |
Gain (loss) recognized in accumulated other comprehensive income | 0 us-gaap_DerivativeInstrumentsGainLossRecognizedInOtherComprehensiveIncomeEffectivePortionNet / us-gaap_DerivativeByNatureAxis = us-gaap_InterestRateContractMember / us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis = us-gaap_CashFlowHedgingMember / us-gaap_HedgingDesignationAxis = us-gaap_DesignatedAsHedgingInstrumentMember | 2 us-gaap_DerivativeInstrumentsGainLossRecognizedInOtherComprehensiveIncomeEffectivePortionNet / us-gaap_DerivativeByNatureAxis = us-gaap_InterestRateContractMember / us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis = us-gaap_CashFlowHedgingMember / us-gaap_HedgingDesignationAxis = us-gaap_DesignatedAsHedgingInstrumentMember | 0 us-gaap_DerivativeInstrumentsGainLossRecognizedInOtherComprehensiveIncomeEffectivePortionNet / us-gaap_DerivativeByNatureAxis = us-gaap_InterestRateContractMember / us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis = us-gaap_CashFlowHedgingMember / us-gaap_HedgingDesignationAxis = us-gaap_DesignatedAsHedgingInstrumentMember
Gain (loss) reclassified from accumulated other comprehensive loss into income (effective portion) | (1)us-gaap_DerivativeInstrumentsGainLossReclassifiedFromAccumulatedOCIIntoIncomeEffectivePortionNet / us-gaap_DerivativeByNatureAxis = us-gaap_InterestRateContractMember / us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis = us-gaap_CashFlowHedgingMember / us-gaap_HedgingDesignationAxis = us-gaap_DesignatedAsHedgingInstrumentMember | (1)us-gaap_DerivativeInstrumentsGainLossReclassifiedFromAccumulatedOCIIntoIncomeEffectivePortionNet / us-gaap_DerivativeByNatureAxis = us-gaap_InterestRateContractMember / us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis = us-gaap_CashFlowHedgingMember / us-gaap_HedgingDesignationAxis = us-gaap_DesignatedAsHedgingInstrumentMember | (1)us-gaap_DerivativeInstrumentsGainLossReclassifiedFromAccumulatedOCIIntoIncomeEffectivePortionNet / us-gaap_DerivativeByNatureAxis = us-gaap_InterestRateContractMember / us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis = us-gaap_CashFlowHedgingMember / us-gaap_HedgingDesignationAxis = us-gaap_DesignatedAsHedgingInstrumentMember
Cash Flow Hedging [Member] | Interest rate contracts [Member] | Compensation and Benefits [Member] |  |  |
Derivative [Line Items] |  |  |
Gain (loss) recognized in accumulated other comprehensive income | 0 us-gaap_DerivativeInstrumentsGainLossRecognizedInOtherComprehensiveIncomeEffectivePortionNet / us-gaap_DerivativeByNatureAxis = us-gaap_InterestRateContractMember / us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis = us-gaap_CashFlowHedgingMember / us-gaap_HedgingDesignationAxis = us-gaap_DesignatedAsHedgingInstrumentMember / us-gaap_IncomeStatementLocationAxis = aon_CompensationandBenefitsMember | 0 us-gaap_DerivativeInstrumentsGainLossRecognizedInOtherComprehensiveIncomeEffectivePortionNet / us-gaap_DerivativeByNatureAxis = us-gaap_InterestRateContractMember / us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis = us-gaap_CashFlowHedgingMember / us-gaap_HedgingDesignationAxis = us-gaap_DesignatedAsHedgingInstrumentMember / us-gaap_IncomeStatementLocationAxis = aon_CompensationandBenefitsMember | 0 us-gaap_DerivativeInstrumentsGainLossRecognizedInOtherComprehensiveIncomeEffectivePortionNet / us-gaap_DerivativeByNatureAxis = us-gaap_InterestRateContractMember / us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis = us-gaap_CashFlowHedgingMember / us-gaap_HedgingDesignationAxis = us-gaap_DesignatedAsHedgingInstrumentMember / us-gaap_IncomeStatementLocationAxis = aon_CompensationandBenefitsMember
Gain (loss) reclassified from accumulated other comprehensive loss into income (effective portion) | 0 us-gaap_DerivativeInstrumentsGainLossReclassifiedFromAccumulatedOCIIntoIncomeEffectivePortionNet / us-gaap_DerivativeByNatureAxis = us-gaap_InterestRateContractMember / us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis = us-gaap_CashFlowHedgingMember / us-gaap_HedgingDesignationAxis = us-gaap_DesignatedAsHedgingInstrumentMember / us-gaap_IncomeStatementLocationAxis = aon_CompensationandBenefitsMember | 0 us-gaap_DerivativeInstrumentsGainLossReclassifiedFromAccumulatedOCIIntoIncomeEffectivePortionNet / us-gaap_DerivativeByNatureAxis = us-gaap_InterestRateContractMember / us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis = us-gaap_CashFlowHedgingMember / us-gaap_HedgingDesignationAxis = us-gaap_DesignatedAsHedgingInstrumentMember / us-gaap_IncomeStatementLocationAxis = aon_CompensationandBenefitsMember | 0 us-gaap_DerivativeInstrumentsGainLossReclassifiedFromAccumulatedOCIIntoIncomeEffectivePortionNet / us-gaap_DerivativeByNatureAxis = us-gaap_InterestRateContractMember / us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis = us-gaap_CashFlowHedgingMember / us-gaap_HedgingDesignationAxis = us-gaap_DesignatedAsHedgingInstrumentMember / us-gaap_IncomeStatementLocationAxis = aon_CompensationandBenefitsMember
Cash Flow Hedging [Member] | Interest rate contracts [Member] | Other General Expenses [Member] |  |  |
Derivative [Line Items] |  |  |
Gain (loss) recognized in accumulated other comprehensive income | 0 us-gaap_DerivativeInstrumentsGainLossRecognizedInOtherComprehensiveIncomeEffectivePortionNet / us-gaap_DerivativeByNatureAxis = us-gaap_InterestRateContractMember / us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis = us-gaap_CashFlowHedgingMember / us-gaap_HedgingDesignationAxis = us-gaap_DesignatedAsHedgingInstrumentMember / us-gaap_IncomeStatementLocationAxis = aon_OtherGeneralExpensesMember | 0 us-gaap_DerivativeInstrumentsGainLossRecognizedInOtherComprehensiveIncomeEffectivePortionNet / us-gaap_DerivativeByNatureAxis = us-gaap_InterestRateContractMember / us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis = us-gaap_CashFlowHedgingMember / us-gaap_HedgingDesignationAxis = us-gaap_DesignatedAsHedgingInstrumentMember / us-gaap_IncomeStatementLocationAxis = aon_OtherGeneralExpensesMember | 0 us-gaap_DerivativeInstrumentsGainLossRecognizedInOtherComprehensiveIncomeEffectivePortionNet / us-gaap_DerivativeByNatureAxis = us-gaap_InterestRateContractMember / us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis = us-gaap_CashFlowHedgingMember / us-gaap_HedgingDesignationAxis = us-gaap_DesignatedAsHedgingInstrumentMember / us-gaap_IncomeStatementLocationAxis = aon_OtherGeneralExpensesMember
Gain (loss) reclassified from accumulated other comprehensive loss into income (effective portion) | 0 us-gaap_DerivativeInstrumentsGainLossReclassifiedFromAccumulatedOCIIntoIncomeEffectivePortionNet / us-gaap_DerivativeByNatureAxis = us-gaap_InterestRateContractMember / us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis = us-gaap_CashFlowHedgingMember / us-gaap_HedgingDesignationAxis = us-gaap_DesignatedAsHedgingInstrumentMember / us-gaap_IncomeStatementLocationAxis = aon_OtherGeneralExpensesMember | 0 us-gaap_DerivativeInstrumentsGainLossReclassifiedFromAccumulatedOCIIntoIncomeEffectivePortionNet / us-gaap_DerivativeByNatureAxis = us-gaap_InterestRateContractMember / us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis = us-gaap_CashFlowHedgingMember / us-gaap_HedgingDesignationAxis = us-gaap_DesignatedAsHedgingInstrumentMember / us-gaap_IncomeStatementLocationAxis = aon_OtherGeneralExpensesMember | 0 us-gaap_DerivativeInstrumentsGainLossReclassifiedFromAccumulatedOCIIntoIncomeEffectivePortionNet / us-gaap_DerivativeByNatureAxis = us-gaap_InterestRateContractMember / us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis = us-gaap_CashFlowHedgingMember / us-gaap_HedgingDesignationAxis = us-gaap_DesignatedAsHedgingInstrumentMember / us-gaap_IncomeStatementLocationAxis = aon_OtherGeneralExpensesMember
Cash Flow Hedging [Member] | Interest rate contracts [Member] | Interest Expense [Member] |  |  |
Derivative [Line Items] |  |  |
Gain (loss) recognized in accumulated other comprehensive income | 0 us-gaap_DerivativeInstrumentsGainLossRecognizedInOtherComprehensiveIncomeEffectivePortionNet / us-gaap_DerivativeByNatureAxis = us-gaap_InterestRateContractMember / us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis = us-gaap_CashFlowHedgingMember / us-gaap_HedgingDesignationAxis = us-gaap_DesignatedAsHedgingInstrumentMember / us-gaap_IncomeStatementLocationAxis = us-gaap_InterestExpenseMember | 2 us-gaap_DerivativeInstrumentsGainLossRecognizedInOtherComprehensiveIncomeEffectivePortionNet / us-gaap_DerivativeByNatureAxis = us-gaap_InterestRateContractMember / us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis = us-gaap_CashFlowHedgingMember / us-gaap_HedgingDesignationAxis = us-gaap_DesignatedAsHedgingInstrumentMember / us-gaap_IncomeStatementLocationAxis = us-gaap_InterestExpenseMember | 0 us-gaap_DerivativeInstrumentsGainLossRecognizedInOtherComprehensiveIncomeEffectivePortionNet / us-gaap_DerivativeByNatureAxis = us-gaap_InterestRateContractMember / us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis = us-gaap_CashFlowHedgingMember / us-gaap_HedgingDesignationAxis = us-gaap_DesignatedAsHedgingInstrumentMember / us-gaap_IncomeStatementLocationAxis = us-gaap_InterestExpenseMember
Gain (loss) reclassified from accumulated other comprehensive loss into income (effective portion) | (1)us-gaap_DerivativeInstrumentsGainLossReclassifiedFromAccumulatedOCIIntoIncomeEffectivePortionNet / us-gaap_DerivativeByNatureAxis = us-gaap_InterestRateContractMember / us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis = us-gaap_CashFlowHedgingMember / us-gaap_HedgingDesignationAxis = us-gaap_DesignatedAsHedgingInstrumentMember / us-gaap_IncomeStatementLocationAxis = us-gaap_InterestExpenseMember | (1)us-gaap_DerivativeInstrumentsGainLossReclassifiedFromAccumulatedOCIIntoIncomeEffectivePortionNet / us-gaap_DerivativeByNatureAxis = us-gaap_InterestRateContractMember / us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis = us-gaap_CashFlowHedgingMember / us-gaap_HedgingDesignationAxis = us-gaap_DesignatedAsHedgingInstrumentMember / us-gaap_IncomeStatementLocationAxis = us-gaap_InterestExpenseMember | (1)us-gaap_DerivativeInstrumentsGainLossReclassifiedFromAccumulatedOCIIntoIncomeEffectivePortionNet / us-gaap_DerivativeByNatureAxis = us-gaap_InterestRateContractMember / us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis = us-gaap_CashFlowHedgingMember / us-gaap_HedgingDesignationAxis = us-gaap_DesignatedAsHedgingInstrumentMember / us-gaap_IncomeStatementLocationAxis = us-gaap_InterestExpenseMember
Cash Flow Hedging [Member] | Interest rate contracts [Member] | Other Income [Member] |  |  |
Derivative [Line Items] |  |  |
Gain (loss) recognized in accumulated other comprehensive income | 0 us-gaap_DerivativeInstrumentsGainLossRecognizedInOtherComprehensiveIncomeEffectivePortionNet / us-gaap_DerivativeByNatureAxis = us-gaap_InterestRateContractMember / us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis = us-gaap_CashFlowHedgingMember / us-gaap_HedgingDesignationAxis = us-gaap_DesignatedAsHedgingInstrumentMember / us-gaap_IncomeStatementLocationAxis = us-gaap_OtherIncomeMember | 0 us-gaap_DerivativeInstrumentsGainLossRecognizedInOtherComprehensiveIncomeEffectivePortionNet / us-gaap_DerivativeByNatureAxis = us-gaap_InterestRateContractMember / us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis = us-gaap_CashFlowHedgingMember / us-gaap_HedgingDesignationAxis = us-gaap_DesignatedAsHedgingInstrumentMember / us-gaap_IncomeStatementLocationAxis = us-gaap_OtherIncomeMember | 0 us-gaap_DerivativeInstrumentsGainLossRecognizedInOtherComprehensiveIncomeEffectivePortionNet / us-gaap_DerivativeByNatureAxis = us-gaap_InterestRateContractMember / us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis = us-gaap_CashFlowHedgingMember / us-gaap_HedgingDesignationAxis = us-gaap_DesignatedAsHedgingInstrumentMember / us-gaap_IncomeStatementLocationAxis = us-gaap_OtherIncomeMember
Gain (loss) reclassified from accumulated other comprehensive loss into income (effective portion) | 0 us-gaap_DerivativeInstrumentsGainLossReclassifiedFromAccumulatedOCIIntoIncomeEffectivePortionNet / us-gaap_DerivativeByNatureAxis = us-gaap_InterestRateContractMember / us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis = us-gaap_CashFlowHedgingMember / us-gaap_HedgingDesignationAxis = us-gaap_DesignatedAsHedgingInstrumentMember / us-gaap_IncomeStatementLocationAxis = us-gaap_OtherIncomeMember | 0 us-gaap_DerivativeInstrumentsGainLossReclassifiedFromAccumulatedOCIIntoIncomeEffectivePortionNet / us-gaap_DerivativeByNatureAxis = us-gaap_InterestRateContractMember / us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis = us-gaap_CashFlowHedgingMember / us-gaap_HedgingDesignationAxis = us-gaap_DesignatedAsHedgingInstrumentMember / us-gaap_IncomeStatementLocationAxis = us-gaap_OtherIncomeMember | 0 us-gaap_DerivativeInstrumentsGainLossReclassifiedFromAccumulatedOCIIntoIncomeEffectivePortionNet / us-gaap_DerivativeByNatureAxis = us-gaap_InterestRateContractMember / us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis = us-gaap_CashFlowHedgingMember / us-gaap_HedgingDesignationAxis = us-gaap_DesignatedAsHedgingInstrumentMember / us-gaap_IncomeStatementLocationAxis = us-gaap_OtherIncomeMember
Cash Flow Hedging [Member] | Foreign Exchange Contract [Member] |  |  |
Derivative [Line Items] |  |  |
Gain (loss) recognized in accumulated other comprehensive income | (2)us-gaap_DerivativeInstrumentsGainLossRecognizedInOtherComprehensiveIncomeEffectivePortionNet / us-gaap_DerivativeByNatureAxis = us-gaap_ForeignExchangeContractMember / us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis = us-gaap_CashFlowHedgingMember / us-gaap_HedgingDesignationAxis = us-gaap_DesignatedAsHedgingInstrumentMember | (4)us-gaap_DerivativeInstrumentsGainLossRecognizedInOtherComprehensiveIncomeEffectivePortionNet / us-gaap_DerivativeByNatureAxis = us-gaap_ForeignExchangeContractMember / us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis = us-gaap_CashFlowHedgingMember / us-gaap_HedgingDesignationAxis = us-gaap_DesignatedAsHedgingInstrumentMember | (21)us-gaap_DerivativeInstrumentsGainLossRecognizedInOtherComprehensiveIncomeEffectivePortionNet / us-gaap_DerivativeByNatureAxis = us-gaap_ForeignExchangeContractMember / us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis = us-gaap_CashFlowHedgingMember / us-gaap_HedgingDesignationAxis = us-gaap_DesignatedAsHedgingInstrumentMember
Gain (loss) reclassified from accumulated other comprehensive loss into income (effective portion) | (14)us-gaap_DerivativeInstrumentsGainLossReclassifiedFromAccumulatedOCIIntoIncomeEffectivePortionNet / us-gaap_DerivativeByNatureAxis = us-gaap_ForeignExchangeContractMember / us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis = us-gaap_CashFlowHedgingMember / us-gaap_HedgingDesignationAxis = us-gaap_DesignatedAsHedgingInstrumentMember | (10)us-gaap_DerivativeInstrumentsGainLossReclassifiedFromAccumulatedOCIIntoIncomeEffectivePortionNet / us-gaap_DerivativeByNatureAxis = us-gaap_ForeignExchangeContractMember / us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis = us-gaap_CashFlowHedgingMember / us-gaap_HedgingDesignationAxis = us-gaap_DesignatedAsHedgingInstrumentMember | (34)us-gaap_DerivativeInstrumentsGainLossReclassifiedFromAccumulatedOCIIntoIncomeEffectivePortionNet / us-gaap_DerivativeByNatureAxis = us-gaap_ForeignExchangeContractMember / us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis = us-gaap_CashFlowHedgingMember / us-gaap_HedgingDesignationAxis = us-gaap_DesignatedAsHedgingInstrumentMember
Cash Flow Hedging [Member] | Foreign Exchange Contract [Member] | Compensation and Benefits [Member] |  |  |
Derivative [Line Items] |  |  |
Gain (loss) recognized in accumulated other comprehensive income | 11 us-gaap_DerivativeInstrumentsGainLossRecognizedInOtherComprehensiveIncomeEffectivePortionNet / us-gaap_DerivativeByNatureAxis = us-gaap_ForeignExchangeContractMember / us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis = us-gaap_CashFlowHedgingMember / us-gaap_HedgingDesignationAxis = us-gaap_DesignatedAsHedgingInstrumentMember / us-gaap_IncomeStatementLocationAxis = aon_CompensationandBenefitsMember | (17)us-gaap_DerivativeInstrumentsGainLossRecognizedInOtherComprehensiveIncomeEffectivePortionNet / us-gaap_DerivativeByNatureAxis = us-gaap_ForeignExchangeContractMember / us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis = us-gaap_CashFlowHedgingMember / us-gaap_HedgingDesignationAxis = us-gaap_DesignatedAsHedgingInstrumentMember / us-gaap_IncomeStatementLocationAxis = aon_CompensationandBenefitsMember | (8)us-gaap_DerivativeInstrumentsGainLossRecognizedInOtherComprehensiveIncomeEffectivePortionNet / us-gaap_DerivativeByNatureAxis = us-gaap_ForeignExchangeContractMember / us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis = us-gaap_CashFlowHedgingMember / us-gaap_HedgingDesignationAxis = us-gaap_DesignatedAsHedgingInstrumentMember / us-gaap_IncomeStatementLocationAxis = aon_CompensationandBenefitsMember
Gain (loss) reclassified from accumulated other comprehensive loss into income (effective portion) | (5)us-gaap_DerivativeInstrumentsGainLossReclassifiedFromAccumulatedOCIIntoIncomeEffectivePortionNet / us-gaap_DerivativeByNatureAxis = us-gaap_ForeignExchangeContractMember / us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis = us-gaap_CashFlowHedgingMember / us-gaap_HedgingDesignationAxis = us-gaap_DesignatedAsHedgingInstrumentMember / us-gaap_IncomeStatementLocationAxis = aon_CompensationandBenefitsMember | (12)us-gaap_DerivativeInstrumentsGainLossReclassifiedFromAccumulatedOCIIntoIncomeEffectivePortionNet / us-gaap_DerivativeByNatureAxis = us-gaap_ForeignExchangeContractMember / us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis = us-gaap_CashFlowHedgingMember / us-gaap_HedgingDesignationAxis = us-gaap_DesignatedAsHedgingInstrumentMember / us-gaap_IncomeStatementLocationAxis = aon_CompensationandBenefitsMember | (9)us-gaap_DerivativeInstrumentsGainLossReclassifiedFromAccumulatedOCIIntoIncomeEffectivePortionNet / us-gaap_DerivativeByNatureAxis = us-gaap_ForeignExchangeContractMember / us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis = us-gaap_CashFlowHedgingMember / us-gaap_HedgingDesignationAxis = us-gaap_DesignatedAsHedgingInstrumentMember / us-gaap_IncomeStatementLocationAxis = aon_CompensationandBenefitsMember
Cash Flow Hedging [Member] | Foreign Exchange Contract [Member] | Other General Expenses [Member] |  |  |
Derivative [Line Items] |  |  |
Gain (loss) recognized in accumulated other comprehensive income | (3)us-gaap_DerivativeInstrumentsGainLossRecognizedInOtherComprehensiveIncomeEffectivePortionNet / us-gaap_DerivativeByNatureAxis = us-gaap_ForeignExchangeContractMember / us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis = us-gaap_CashFlowHedgingMember / us-gaap_HedgingDesignationAxis = us-gaap_DesignatedAsHedgingInstrumentMember / us-gaap_IncomeStatementLocationAxis = aon_OtherGeneralExpensesMember | 0 us-gaap_DerivativeInstrumentsGainLossRecognizedInOtherComprehensiveIncomeEffectivePortionNet / us-gaap_DerivativeByNatureAxis = us-gaap_ForeignExchangeContractMember / us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis = us-gaap_CashFlowHedgingMember / us-gaap_HedgingDesignationAxis = us-gaap_DesignatedAsHedgingInstrumentMember / us-gaap_IncomeStatementLocationAxis = aon_OtherGeneralExpensesMember | (19)us-gaap_DerivativeInstrumentsGainLossRecognizedInOtherComprehensiveIncomeEffectivePortionNet / us-gaap_DerivativeByNatureAxis = us-gaap_ForeignExchangeContractMember / us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis = us-gaap_CashFlowHedgingMember / us-gaap_HedgingDesignationAxis = us-gaap_DesignatedAsHedgingInstrumentMember / us-gaap_IncomeStatementLocationAxis = aon_OtherGeneralExpensesMember
Gain (loss) reclassified from accumulated other comprehensive loss into income (effective portion) | 3 us-gaap_DerivativeInstrumentsGainLossReclassifiedFromAccumulatedOCIIntoIncomeEffectivePortionNet / us-gaap_DerivativeByNatureAxis = us-gaap_ForeignExchangeContractMember / us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis = us-gaap_CashFlowHedgingMember / us-gaap_HedgingDesignationAxis = us-gaap_DesignatedAsHedgingInstrumentMember / us-gaap_IncomeStatementLocationAxis = aon_OtherGeneralExpensesMember | (9)us-gaap_DerivativeInstrumentsGainLossReclassifiedFromAccumulatedOCIIntoIncomeEffectivePortionNet / us-gaap_DerivativeByNatureAxis = us-gaap_ForeignExchangeContractMember / us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis = us-gaap_CashFlowHedgingMember / us-gaap_HedgingDesignationAxis = us-gaap_DesignatedAsHedgingInstrumentMember / us-gaap_IncomeStatementLocationAxis = aon_OtherGeneralExpensesMember | (16)us-gaap_DerivativeInstrumentsGainLossReclassifiedFromAccumulatedOCIIntoIncomeEffectivePortionNet / us-gaap_DerivativeByNatureAxis = us-gaap_ForeignExchangeContractMember / us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis = us-gaap_CashFlowHedgingMember / us-gaap_HedgingDesignationAxis = us-gaap_DesignatedAsHedgingInstrumentMember / us-gaap_IncomeStatementLocationAxis = aon_OtherGeneralExpensesMember
Cash Flow Hedging [Member] | Foreign Exchange Contract [Member] | Interest Expense [Member] |  |  |
Derivative [Line Items] |  |  |
Gain (loss) recognized in accumulated other comprehensive income | 0 us-gaap_DerivativeInstrumentsGainLossRecognizedInOtherComprehensiveIncomeEffectivePortionNet / us-gaap_DerivativeByNatureAxis = us-gaap_ForeignExchangeContractMember / us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis = us-gaap_CashFlowHedgingMember / us-gaap_HedgingDesignationAxis = us-gaap_DesignatedAsHedgingInstrumentMember / us-gaap_IncomeStatementLocationAxis = us-gaap_InterestExpenseMember | 0 us-gaap_DerivativeInstrumentsGainLossRecognizedInOtherComprehensiveIncomeEffectivePortionNet / us-gaap_DerivativeByNatureAxis = us-gaap_ForeignExchangeContractMember / us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis = us-gaap_CashFlowHedgingMember / us-gaap_HedgingDesignationAxis = us-gaap_DesignatedAsHedgingInstrumentMember / us-gaap_IncomeStatementLocationAxis = us-gaap_InterestExpenseMember | 0 us-gaap_DerivativeInstrumentsGainLossRecognizedInOtherComprehensiveIncomeEffectivePortionNet / us-gaap_DerivativeByNatureAxis = us-gaap_ForeignExchangeContractMember / us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis = us-gaap_CashFlowHedgingMember / us-gaap_HedgingDesignationAxis = us-gaap_DesignatedAsHedgingInstrumentMember / us-gaap_IncomeStatementLocationAxis = us-gaap_InterestExpenseMember
Gain (loss) reclassified from accumulated other comprehensive loss into income (effective portion) | (10)us-gaap_DerivativeInstrumentsGainLossReclassifiedFromAccumulatedOCIIntoIncomeEffectivePortionNet / us-gaap_DerivativeByNatureAxis = us-gaap_ForeignExchangeContractMember / us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis = us-gaap_CashFlowHedgingMember / us-gaap_HedgingDesignationAxis = us-gaap_DesignatedAsHedgingInstrumentMember / us-gaap_IncomeStatementLocationAxis = us-gaap_InterestExpenseMember | (3)us-gaap_DerivativeInstrumentsGainLossReclassifiedFromAccumulatedOCIIntoIncomeEffectivePortionNet / us-gaap_DerivativeByNatureAxis = us-gaap_ForeignExchangeContractMember / us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis = us-gaap_CashFlowHedgingMember / us-gaap_HedgingDesignationAxis = us-gaap_DesignatedAsHedgingInstrumentMember / us-gaap_IncomeStatementLocationAxis = us-gaap_InterestExpenseMember | 0 us-gaap_DerivativeInstrumentsGainLossReclassifiedFromAccumulatedOCIIntoIncomeEffectivePortionNet / us-gaap_DerivativeByNatureAxis = us-gaap_ForeignExchangeContractMember / us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis = us-gaap_CashFlowHedgingMember / us-gaap_HedgingDesignationAxis = us-gaap_DesignatedAsHedgingInstrumentMember / us-gaap_IncomeStatementLocationAxis = us-gaap_InterestExpenseMember
Cash Flow Hedging [Member] | Foreign Exchange Contract [Member] | Other Income [Member] |  |  |
Derivative [Line Items] |  |  |
Gain (loss) recognized in accumulated other comprehensive income | (10)us-gaap_DerivativeInstrumentsGainLossRecognizedInOtherComprehensiveIncomeEffectivePortionNet / us-gaap_DerivativeByNatureAxis = us-gaap_ForeignExchangeContractMember / us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis = us-gaap_CashFlowHedgingMember / us-gaap_HedgingDesignationAxis = us-gaap_DesignatedAsHedgingInstrumentMember / us-gaap_IncomeStatementLocationAxis = us-gaap_OtherIncomeMember | 13 us-gaap_DerivativeInstrumentsGainLossRecognizedInOtherComprehensiveIncomeEffectivePortionNet / us-gaap_DerivativeByNatureAxis = us-gaap_ForeignExchangeContractMember / us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis = us-gaap_CashFlowHedgingMember / us-gaap_HedgingDesignationAxis = us-gaap_DesignatedAsHedgingInstrumentMember / us-gaap_IncomeStatementLocationAxis = us-gaap_OtherIncomeMember | 6 us-gaap_DerivativeInstrumentsGainLossRecognizedInOtherComprehensiveIncomeEffectivePortionNet / us-gaap_DerivativeByNatureAxis = us-gaap_ForeignExchangeContractMember / us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis = us-gaap_CashFlowHedgingMember / us-gaap_HedgingDesignationAxis = us-gaap_DesignatedAsHedgingInstrumentMember / us-gaap_IncomeStatementLocationAxis = us-gaap_OtherIncomeMember
Gain (loss) reclassified from accumulated other comprehensive loss into income (effective portion) | (2)us-gaap_DerivativeInstrumentsGainLossReclassifiedFromAccumulatedOCIIntoIncomeEffectivePortionNet / us-gaap_DerivativeByNatureAxis = us-gaap_ForeignExchangeContractMember / us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis = us-gaap_CashFlowHedgingMember / us-gaap_HedgingDesignationAxis = us-gaap_DesignatedAsHedgingInstrumentMember / us-gaap_IncomeStatementLocationAxis = us-gaap_OtherIncomeMember | 14 us-gaap_DerivativeInstrumentsGainLossReclassifiedFromAccumulatedOCIIntoIncomeEffectivePortionNet / us-gaap_DerivativeByNatureAxis = us-gaap_ForeignExchangeContractMember / us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis = us-gaap_CashFlowHedgingMember / us-gaap_HedgingDesignationAxis = us-gaap_DesignatedAsHedgingInstrumentMember / us-gaap_IncomeStatementLocationAxis = us-gaap_OtherIncomeMember | (9)us-gaap_DerivativeInstrumentsGainLossReclassifiedFromAccumulatedOCIIntoIncomeEffectivePortionNet / us-gaap_DerivativeByNatureAxis = us-gaap_ForeignExchangeContractMember / us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis = us-gaap_CashFlowHedgingMember / us-gaap_HedgingDesignationAxis = us-gaap_DesignatedAsHedgingInstrumentMember / us-gaap_IncomeStatementLocationAxis = us-gaap_OtherIncomeMember
Net Investment Hedging [Member] | Foreign Exchange Contract [Member] |  |  |
Derivative [Line Items] |  |  |
Gain (loss) recognized in accumulated other comprehensive income |  |  | 4 us-gaap_DerivativeInstrumentsGainLossRecognizedInOtherComprehensiveIncomeEffectivePortionNet / us-gaap_DerivativeByNatureAxis = us-gaap_ForeignExchangeContractMember / us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis = us-gaap_NetInvestmentHedgingMember / us-gaap_HedgingDesignationAxis = us-gaap_DesignatedAsHedgingInstrumentMember
Net Investment Hedging [Member] | Foreign Exchange Contract [Member] | Compensation and Benefits [Member] |  |  |
Derivative [Line Items] |  |  |
Gain (loss) recognized in accumulated other comprehensive income |  |  | 0 us-gaap_DerivativeInstrumentsGainLossRecognizedInOtherComprehensiveIncomeEffectivePortionNet / us-gaap_DerivativeByNatureAxis = us-gaap_ForeignExchangeContractMember / us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis = us-gaap_NetInvestmentHedgingMember / us-gaap_HedgingDesignationAxis = us-gaap_DesignatedAsHedgingInstrumentMember / us-gaap_IncomeStatementLocationAxis = aon_CompensationandBenefitsMember
Net Investment Hedging [Member] | Foreign Exchange Contract [Member] | Other General Expenses [Member] |  |  |
Derivative [Line Items] |  |  |
Gain (loss) recognized in accumulated other comprehensive income |  |  | 0 us-gaap_DerivativeInstrumentsGainLossRecognizedInOtherComprehensiveIncomeEffectivePortionNet / us-gaap_DerivativeByNatureAxis = us-gaap_ForeignExchangeContractMember / us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis = us-gaap_NetInvestmentHedgingMember / us-gaap_HedgingDesignationAxis = us-gaap_DesignatedAsHedgingInstrumentMember / us-gaap_IncomeStatementLocationAxis = aon_OtherGeneralExpensesMember
Net Investment Hedging [Member] | Foreign Exchange Contract [Member] | Interest Expense [Member] |  |  |
Derivative [Line Items] |  |  |
Gain (loss) recognized in accumulated other comprehensive income |  |  | 0 us-gaap_DerivativeInstrumentsGainLossRecognizedInOtherComprehensiveIncomeEffectivePortionNet / us-gaap_DerivativeByNatureAxis = us-gaap_ForeignExchangeContractMember / us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis = us-gaap_NetInvestmentHedgingMember / us-gaap_HedgingDesignationAxis = us-gaap_DesignatedAsHedgingInstrumentMember / us-gaap_IncomeStatementLocationAxis = us-gaap_InterestExpenseMember
Net Investment Hedging [Member] | Foreign Exchange Contract [Member] | Other Income [Member] |  |  |
Derivative [Line Items] |  |  |
Gain (loss) recognized in accumulated other comprehensive income |  |  | $ 4 us-gaap_DerivativeInstrumentsGainLossRecognizedInOtherComprehensiveIncomeEffectivePortionNet / us-gaap_DerivativeByNatureAxis = us-gaap_ForeignExchangeContractMember / us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis = us-gaap_NetInvestmentHedgingMember / us-gaap_HedgingDesignationAxis = us-gaap_DesignatedAsHedgingInstrumentMember / us-gaap_IncomeStatementLocationAxis = us-gaap_OtherIncomeMember

X
- Definition The effective portion of net gain (loss) reclassified from accumulated other comprehensive income into income on derivative instruments designated and qualifying as hedging instruments. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 4C -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=7476318&loc=SL5624171-113959 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 4D -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=7476318&loc=SL5624177-113959 + Details
Name: | us-gaap_DerivativeInstrumentsGainLossReclassifiedFromAccumulatedOCIIntoIncomeEffectivePortionNet
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition The effective portion of gains and losses (net) on derivative instruments designated and qualifying as hedging instruments that was recognized in other comprehensive income during the current period. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 4C -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=7476318&loc=SL5624171-113959 + Details
Name: | us-gaap_DerivativeInstrumentsGainLossRecognizedInOtherComprehensiveIncomeEffectivePortionNet
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Details
Name: | us-gaap_DerivativeLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration