Condensed Consolidated Statements of Income (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended				9 Months Ended
	Sep. 30, 2013		Sep. 30, 2012		Sep. 30, 2013		Sep. 30, 2012
Revenue
Commissions, fees and other	$ 2,786		$ 2,726		$ 8,585		$ 8,368
Fiduciary investment income	8		11		21		31
Total revenue	2,794		2,737		8,606		8,399
Expenses
Compensation and benefits	1,666		1,620		5,103		4,920
Other general expenses	764		778		2,347		2,344
Total operating expenses	2,430		2,398		7,450		7,264
Operating income	364		339		1,156		1,135
Interest income	3		1		6		6
Interest expense	(53)		(57)		(153)		(173)
Other income (expense)	39		(9)		54		3
Income from continuing operations before income taxes	353		274		1,063		971
Income taxes	89		64		275		257
Income from continuing operations	264		210		788		714
Loss from discontinued operations before income taxes	0		0		0		(1)
Income taxes	0		0		0		0
Loss from discontinued operations	0		0		0		(1)
Net income	264		210		788		713
Less: Net income attributable to noncontrolling interests	8		6		30		25
Net income attributable to Aon shareholders	256		204		758		688
Net income (loss) attributable to Aon shareholders
Income from continuing operations	256		204		758		689
Loss from discontinued operations	0		0		0		(1)
Net income attributable to Aon shareholders	$ 256		$ 204		$ 758		$ 688
Basic net income per share attributable to Aon shareholders
Continuing operations (in dollars per share)	$ 0.83		$ 0.62		$ 2.42		$ 2.08
Discontinued operations (in dollars per share)	$ 0.00		$ 0.00		$ 0.00		$ 0.00
Net income (in dollars per share)	$ 0.83		$ 0.62		$ 2.42		$ 2.08
Diluted net income per share attributable to Aon shareholders
Continuing operations (in dollars per share)	$ 0.82		$ 0.62		$ 2.39		$ 2.06
Discontinued operations (in dollars per share)	$ 0.00		$ 0.00		$ 0.00		$ 0.00
Net income (in dollars per share)	$ 0.82		$ 0.62		$ 2.39		$ 2.06
Cash dividends per share paid on ordinary shares (in dollars per share)	$ 0.18		$ 0.16		$ 0.51		$ 0.46
Weighted average ordinary shares outstanding - basic	309.5	[1]	327.3	[1]	313.2	[1]	330.6	[1]
Weighted average ordinary shares outstanding - diluted	312.9		331.0		316.7		334.4

[1] Includes 3.8 million and 4.5 million of participating securities for the three months ended September 30, 2013 and 2012, respectively, and 4.0 million and 4.7 million of participating securities for the nine months ended September 30, 2013 and 2012, respectively.