Equity, Stock Repurchase Activities (Details) (USD $) Share data in Millions, except Per Share data	3 Months Ended						9 Months Ended
	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Sep. 30, 2010	Jun. 30, 2010	Mar. 31, 2010	Sep. 30, 2011	Sep. 30, 2010
Stock Repurchased and Retired During Period, Shares	8.9			5.0			17.5	14.3
Common Stock Repurchased Under Stock Repurchase Program Average Purchase Price	$ 21.47			$ 26.81			$ 30.93	$ 27.09
Common stock repurchased and retired under stock repurchase programs, value	$ 191,000,000	$ 150,000,000	$ 200,200,000	$ 134,900,000	$ 177,400,000	$ 74,400,000	$ 541,200,000	$ 386,700,000
Stock Repurchase Program 2008 [Member]
Common stock authorized for repurchase under the 2010 and 2008 Stock Repurchase Programs	1,000,000,000
Stock Repurchase Program, Remaining Authorized Repurchase Amount							0
Stock Repurchase Program 2010 [Member]
Common stock authorized for repurchase under the 2010 and 2008 Stock Repurchase Programs	1,000,000,000
Stock Repurchase Program, Remaining Authorized Repurchase Amount							$ 213,800,000