Stockholders’ Equity - Summary of Stock Repurchase Activity (Details) $ / shares in Units, $ in Millions	6 Months Ended
	Jun. 30, 2017 USD ($) $ / shares shares
Equity [Abstract]
Shares Repurchased | shares	25,000,000
Average Price per Share (in usd per share) | $ / shares	$ 33.73
Value of Shares Repurchased	$ 857
Shares Repurchased, Remaining Amount Authorized
Beginning balance	1,336
Repurchase of shares of common stock	(857)
Ending balance	$ 479
Treasury shares retired | shares	0