v2.3.0.15

Acquisitions and Dispositions (Details 4) (USD $) In Millions, unless otherwise specified	3 Months Ended	9 Months Ended
	Sep. 30, 2010	Sep. 30, 2011 year month segment entity	Sep. 30, 2010
Dispositions discontinued operations
Income (loss) from discontinued operations before income taxes	$ 1	$ 5	$ (38)
Dispositions continuing operations
Number of divestitures		2
Aggregate pretax loss on disposition of continuing operations		$ 1.8

X

- Definition

The aggregate gain (loss) from the date of the agreement to the final disposition, resulting from the sale of a disposal group that is not a discontinued operation. It is included in income from continuing operations before income taxes in the income statement.

+ Details

Name:	aon_DisposalGroupNotDiscontinuedOperationAggregateGainLossOnDisposal
Namespace Prefix:	aon
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

X

- Details

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

X

- Details

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

X

- Definition

Represents the number of entities disposed of by the reporting entity.

+ Details

Name:	aon_NumberOfDispositions
Namespace Prefix:	aon
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

X

- Definition

Overall income (loss) from a disposal group that is classified as a component of the entity, before income tax, reported as a separate component of income before extraordinary items and the cumulative effect of accounting changes. Includes the following (before income tax): income (loss) from operations during the phase-out period, gain (loss) on disposal, provision (or any reversals of earlier provisions) for loss on disposal, and adjustments of a prior period gain (loss) on disposal.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 05

-Paragraph 15

-Article 3



Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 144

-Paragraph 43



Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 144

-Paragraph 47

-Subparagraph c



Reference 4: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 04

-Paragraph 13

-Article 7

+ Details

Name:	us-gaap_DiscontinuedOperationIncomeLossFromDiscontinuedOperationBeforeIncomeTax
Namespace Prefix:	us-gaap
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration