Condensed Consolidated Statements of Income (USD $) In Millions, except Per Share data	3 Months Ended		9 Months Ended
	Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2011	Sep. 30, 2010
Revenue
Commissions, fees and other	$ 2,708	$ 1,786	$ 8,255	$ 5,560
Fiduciary investment income	15	15	38	43
Total revenue	2,723	1,801	8,293	5,603
Expenses
Compensation and benefits	1,634	1,050	4,843	3,382
Other general expenses	748	488	2,279	1,417
Total operating expenses	2,382	1,538	7,122	4,799
Operating income	341	263	1,171	804
Interest income	4	4	14	9
Interest expense	(60)	(50)	(186)	(117)
Other income (expense)	7	(9)	1	3
Income from continuing operations before income taxes	292	208	1,000	699
Income taxes	84	61	274	182
Income from continuing operations	208	147	726	517
Income (loss) from discontinued operations before income taxes		1	5	(38)
Income taxes		1	1	(12)
Income (loss) from discontinued operations			4	(26)
Net income	208	147	730	491
Less: Net income attributable to noncontrolling interests	10	3	28	16
Net income attributable to Aon stockholders	198	144	702	475
Net income (loss) attributable to Aon stockholders
Income from continuing operations	198	144	698	501
Income (loss) from discontinued operations			4	(26)
Net income attributable to Aon stockholders	$ 198	$ 144	$ 702	$ 475
Basic net income (loss) per share attributable to Aon stockholders
Continuing operations (in dollars per share)	$ 0.59	$ 0.52	$ 2.07	$ 1.80
Discontinued operations (in dollars per share)			$ 0.01	$ (0.09)
Net income (in dollars per share)	$ 0.59	$ 0.52	$ 2.08	$ 1.71
Diluted net income (loss) per share attributable to Aon stockholders
Continuing operations (in dollars per share)	$ 0.59	$ 0.51	$ 2.04	$ 1.78
Discontinued operations (in dollars per share)			$ 0.01	$ (0.10)
Net income (in dollars per share)	$ 0.59	$ 0.51	$ 2.05	$ 1.68
Cash dividends per share paid on common stock (in dollars per share)	$ 0.15	$ 0.15	$ 0.45	$ 0.45
Weighted average common shares outstanding - basic (in shares)	332.6	278.7	336.7	277.6
Weighted average common shares outstanding - diluted (in shares)	336.9	282.2	341.8	281.9