Equity, Stock Repurchase Activities (Details) (USD $) Share data in Millions, except Per Share data, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Stock Repurchased and Retired During Period, Shares	5.0	3.9	7.4	8.6
Common Stock Repurchased Under Stock Repurchase Program Average Purchase Price	$ 18.76	$ 38.94	$ 19.72	$ 40.71
Common stock repurchased and retired under stock repurchase programs, value	$ 94,000,000	$ 150,000,000	$ 145,600,000	$ 350,200,000
Stock Repurchase Program, Remaining Authorized Repurchase Amount			1,100,000,000
2010 Stock Repurchase Program [Member]
Stock Repurchase Program, Authorized Amount			1,000,000,000
2012 Stock Repurchase Program [Member]
Stock Repurchase Program, Authorized Amount			$ 1,000,000,000