v2.3.0.15

Commitments and Contingencies (Details 2) (USD $) In Millions, unless otherwise specified	Sep. 30, 2011 plan	Dec. 31, 2010
Commitments and Contingencies
Letters of credit outstanding	$ 76	$ 71
Number of US pension plans that are a LOC beneficiary	1

X

- Details

Name:	aon_CommitmentsAndContingenciesDisclosureAbstract
Namespace Prefix:	aon
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

X

- Definition

The total amount of the contingent obligation under letters of credit outstanding as of the reporting date.

+ Details

Name:	aon_LettersOfCreditOutstandingAmount
Namespace Prefix:	aon
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

X

- Definition

The number of US pension plans that are a beneficiary under letters of credit outstanding as of the reporting date.

+ Details

Name:	aon_LettersOfCreditPensionPlanBeneficiary
Namespace Prefix:	aon
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant