Common Stock (Details) (USD $) Share data in Millions, unless otherwise specified	1 Months Ended	6 Months Ended
	May 31, 2014	Jun. 30, 2014	Jun. 30, 2013
Equity, Class of Treasury Stock [Line Items]
Payments for repurchase of common stock		$ 350,000,000	$ 250,000,000
Common Stock [Member]
Equity, Class of Treasury Stock [Line Items]
Common stock repurchased (in shares)		7.0	6.4
Share repurchases program, authorized amount	2,000,000,000
Stock repurchase program, remaining authorized repurchase amount		$ 1,800,000,000