Common Stock (Details) - USD ($) shares in Millions	9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	May 31, 2015
Equity, Class of Treasury Stock [Line Items]
Payments for repurchase of common stock	$ 625,000,000	$ 1,325,000,000
Common Stock
Equity, Class of Treasury Stock [Line Items]
Common stock repurchased (in shares)	10.0	23.4
Payments for repurchase of common stock	$ 625,000,000
Share repurchases program, authorized amount (up to)			$ 2,000,000,000
Stock repurchase program, remaining authorized repurchase amount	$ 530,000,000