Consolidated Statements of Income (USD $) In Millions, except Per Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Revenue
Commissions, fees and other	$ 11,476	$ 11,235	$ 8,457
Fiduciary investment income	38	52	55
Total revenue	11,514	11,287	8,512
Expenses
Compensation and benefits	6,709	6,567	5,097
Other general expenses	3,209	3,124	2,171
Total operating expenses	9,918	9,691	7,268
Operating income	1,596	1,596	1,244
Interest income	10	18	15
Interest expense	(228)	(245)	(182)
Other income (expense)	3	15	(18)
Income from continuing operations before income taxes	1,381	1,384	1,059
Income taxes	360	378	300
Income from continuing operations	1,021	1,006	759
(Loss) income from discontinued operations before income taxes	(1)	5	(39)
Income taxes (benefit)		1	(12)
(Loss) income from discontinued operations	(1)	4	(27)
Net income	1,020	1,010	732
Less: Net income attributable to noncontrolling interests	27	31	26
Net income attributable to Aon shareholders	993	979	706
Net income attributable to Aon shareholders
Income from continuing operations	994	975	733
(Loss) income from discontinued operations	(1)	4	(27)
Net income	$ 993	$ 979	$ 706
Basic net income (loss) per share attributable to Aon shareholders
Continuing operations (in dollars per share)	$ 3.03	$ 2.91	$ 2.50
Discontinued operations (in dollars per share)		$ 0.01	$ (0.09)
Net income (in dollars per share)	$ 3.03	$ 2.92	$ 2.41
Diluted net income (loss) per share attributable to Aon shareholders
Continuing operations (in dollars per share)	$ 2.99	$ 2.86	$ 2.46
Discontinued operations (in dollars per share)		$ 0.01	$ (0.09)
Net income (in dollars per share)	$ 2.99	$ 2.87	$ 2.37
Cash dividends per share paid on ordinary shares (in dollars per share)	$ 0.62	$ 0.60	$ 0.60
Weighted average ordinary shares outstanding - basic (in shares)	328.5	335.5	293.4
Weighted average ordinary shares outstanding - diluted (in shares)	332.6	340.9	298.1