Common Stock (Details) - USD ($) shares in Millions	6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014
Equity, Class of Treasury Stock [Line Items]
Payments for repurchase of common stock	$ 775,000,000	$ 350,000,000
Common Stock [Member]
Equity, Class of Treasury Stock [Line Items]
Common stock repurchased (in shares)	13.5	7.0
Share repurchases program, authorized amount	$ 2,000,000,000
Stock repurchase program, remaining authorized repurchase amount	$ 1,800,000,000