Subsequent Events (Details) (USD $) Share data in Millions	1 Months Ended		3 Months Ended	4 Months Ended	9 Months Ended
	Oct. 31, 2011	Aug. 31, 2011	Sep. 30, 2011	Oct. 31, 2011	Sep. 30, 2011
Subsequent Events
Common stock repurchase program, authorized amount		$ 1,500,000,000
Number of shares repurchased (in shares)	0.9		5.6	6.5
Purchase of treasury stock value	121,700,000		878,400,000	1,000,000,000	878,400,000
Liability for treasury stock repurchase			76,500,000		76,500,000
Repurchase of Common Stock
Subsequent Events
Common stock repurchase program, authorized amount		1,500,000,000
Number of shares repurchased (in shares)	0.9		5.6	6.5
Purchase of treasury stock value	$ 121,700,000		$ 878,400,000	$ 1,000,000,000