XML 52 R59.htm IDEA: XBRL DOCUMENT
v2.4.1.9

Derivatives and Hedging Interest Rate Management Risk Narrative (Details) (USD $) In Millions, unless otherwise specified | 3 Months Ended
--- | ---
Mar. 31, 2015 | Mar. 31, 2014
Derivative [Line Items] |  |
Estimated pretax losses currently included within Accumulated Other Comprehensive Loss that will be reclassified to earnings in next twelve months | $ 4 aon_HedgeGainLossToBeReclassifiedDuringNext12Months |
Derivative gain (loss) | (1)us-gaap_DerivativeGainLossOnDerivativeNet | (23)us-gaap_DerivativeGainLossOnDerivativeNet
Not Designated as Hedging Instrument [Member] | Foreign exchange contracts [Member] |  |
Derivative [Line Items] |  |
Derivative gain (loss) | $ 7 us-gaap_DerivativeGainLossOnDerivativeNet / us-gaap_DerivativeByNatureAxis = us-gaap_ForeignExchangeContractMember / us-gaap_HedgingDesignationAxis = us-gaap_NondesignatedMember | $ (5)us-gaap_DerivativeGainLossOnDerivativeNet / us-gaap_DerivativeByNatureAxis = us-gaap_ForeignExchangeContractMember / us-gaap_HedgingDesignationAxis = us-gaap_NondesignatedMember
Cash Flow Hedging [Member] |  |
Derivative [Line Items] |  |
Interest rate fluctuations, maximum hedging period | 2 years |

X
- Definition Represents the estimated net amount of unrealized gains (losses) on hedges at the reporting date expected to be reclassified to earnings within the next 12 months. + References No definition available. + Details
Name: | aon_HedgeGainLossToBeReclassifiedDuringNext12Months
Namespace Prefix: | aon_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Amount of increase (decrease) in the fair value of derivatives recognized in the income statement. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 4A -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=56946850&loc=SL5618551-113959 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 4C -Subparagraph (a),(c),(d),(e) -URI http://asc.fasb.org/extlink&oid=56946850&loc=SL5624171-113959 + Details
Name: | us-gaap_DerivativeGainLossOnDerivativeNet
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

X
- Definition Maximum period the entity is hedging its exposure to the variability in future cash flows for forecasted transactions, excluding those forecasted transactions related to the payment of variable interest on existing financial instruments, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 30 -Section 50 -Paragraph 1 -Subparagraph (d) -URI http://asc.fasb.org/extlink&oid=35736893&loc=d3e80748-113994 + Details
Name: | us-gaap_MaximumLengthOfTimeHedgedInInterestRateCashFlowHedge1
Namespace Prefix: | us-gaap_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

X
- Details
Name: | us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis=us-gaap_CashFlowHedgingMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_HedgingDesignationAxis=us-gaap_NondesignatedMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |