Condensed Consolidated Statements of Comprehensive Income (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011
Net income	$ 249	$ 255
Less: Net income attributable to noncontrolling interests	11	9
Net income attributable to Aon stockholders	238	246
Other comprehensive income, net of tax:
Change in derivative gains/losses	7	(4)
Foreign currency translation adjustments	104	195
Post-retirement benefit obligation	21	12
Total other comprehensive income, net of tax	132	203
Less: Other comprehensive income attributable to noncontrolling interests	1
Total other comprehensive income attributable to Aon stockholders	131	203
Comprehensive income attributable to Aon stockholders	$ 369	$ 449