Common Stock (Details) (USD $) Share data in Millions, unless otherwise specified	12 Months Ended			1 Months Ended	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	May 31, 2013 Common Stock [Member]	Dec. 31, 2013 Common Stock [Member]	Dec. 31, 2012 Common Stock [Member]
Equity, Class of Treasury Stock [Line Items]
Common stock repurchased					13.2	6.9
Payments for repurchase of common stock	$ 550,000,000	$ 230,000,000	$ 361,000,000
Stock repurchase program, authorized amount				1,000,000,000
Stock repurchase program, remaining authorized repurchase amount					$ 563,000,000