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
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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
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Namespace Prefix: | aon
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X
- Definition The number of US pension plans that are a beneficiary under letters of credit outstanding as of the reporting date. + Details
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Namespace Prefix: | aon
Data Type: | xbrli:integerItemType
Balance Type: | na
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