Acquisitions and Dispositions - Dispositions (Details) (USD $)	3 Months Ended	6 Months Ended
Jun. 30, 2014 business	Jun. 30, 2014 Risk Solutions [Member] business	Jun. 30, 2013 Risk Solutions [Member] business
Dispositions
Number of dispositions	0	1	4
Gain (loss) recognized on sale		$ 1,000,000	$ 0

The gain (loss) resulting from the sale of a disposal group that is not a discontinued operation and other income. It is included in income from continuing operations before income taxes in the income statement.

No definition available.

Name:	aon_DisposalGroupNotDiscontinuedOperationGainLossOnDisposalAndOther
Namespace Prefix:	aon_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration