Subsequent Events (Details) (USD $) Share data in Millions, except Per Share data, unless otherwise specified	3 Months Ended		9 Months Ended		1 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012	Nov. 08, 2013 Subsequent event
Subsequent Event [Line Items]
Stock repurchased during period, shares					0.3
Stock repurchased during period, value					$ 7,000,000
Common stock repurchased under stock repurchase program average purchase price	$ 20.92	$ 18.00	$ 19.32	$ 18.60	$ 20.19
Stock repurchased and retired during period, shares	4.4	13.9	17.0	21.3	0.3
Stock repurchase program, remaining authorized repurchase amount			$ 1,200,000,000		$ 1,200,000,000