Subsequent Events (Details) (USD $) Share data in Millions, except Per Share data, unless otherwise specified	3 Months Ended		6 Months Ended		1 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012	Aug. 08, 2013 Subsequent Event [Member]
Subsequent Event [Line Items]
Stock repurchase program, Authorized amount			$ 1,000,000,000		$ 1,000,000,000
Stock repurchased during period, shares					1.6
Stock repurchased during period, value					34,100,000
Common stock repurchased under stock repurchase program average purchase price	$ 16.45	$ 18.76	$ 18.68	$ 19.72	$ 21.74
Stock repurchased and retired during period, shares	6.4	5.0	12.6	7.4	1.3
Stock repurchase program, remaining authorized repurchase amount			$ 332,800,000		$ 298,700,000