Stockholders' Equity (Details) (USD $) Share data in Millions, except Per Share data	9 Months Ended		3 Months Ended	9 Months Ended		9 Months Ended		9 Months Ended
	Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2011 2010 Stock Repurchase Program	Sep. 30, 2011 2010 Stock Repurchase Program	Jan. 31, 2010 2010 Stock Repurchase Program	Sep. 30, 2010 2007 - Share Repurchase Program	Dec. 31, 2007 2007 - Share Repurchase Program	Sep. 30, 2011 Hewitt Associates, Inc (Hewitt)
Common Stock Programs
Share repurchase authorization limit (in dollars)					$ 2,000,000,000		$ 4,600,000,000
Number of shares repurchased			3.8	16.4		2.4
Average price per share of shares purchased under share repurchase program (in dollars per share)			$ 45.61	$ 50.39
Cost of shares repurchased (in dollars)	828,000,000		175,000,000	828,000,000		100,000,000
Cumulative number of shares purchased under share repurchase programs	128.3
Cumulative value of shares purchased under share repurchase programs (in dollars)	5,400,000,000
Additional share repurchase authorization limit (in dollars)			$ 1,200,000,000	$ 1,200,000,000
Number of shares issued for options exercised as part of the Hewitt acquisition								0.5
Number of treasury shares reissued for employee benefit plans	6.7	6.8
Number of treasury shares reissued for employee stock purchase plans	0.2	0.3