Basis of Presentation (Details) (USD $)	0 Months Ended
Apr. 02, 2012 subsidiary
Company Redomestication
Number of Subsidiaries	1
Right to receive number of Class A Ordinary Share in redomestication	1
Nominal value of Class A Ordinary Share in redomestication (in dollars per share)	$ 0.01

Represents the nominal value of shares of common stock in redomestication.

No definition available.

Name:	aon_RightToReceiveCommonStockInRedomesticationNominalValuePerShare
Namespace Prefix:	aon_
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	duration