Common Stock (Details) - USD ($) shares in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016	Nov. 30, 2016
Equity, Class of Treasury Stock [Line Items]
Payments for repurchase of common stock	$ 200,000,000	$ 200,000,000
Common Stock
Equity, Class of Treasury Stock [Line Items]
Common stock repurchased (in shares)	2.7	3.5
Payments for repurchase of common stock	$ 200,000,000
Share repurchases program, authorized amount (up to)			$ 2,500,000,000.0
Stock repurchase program, remaining authorized repurchase amount	$ 2,200,000,000