Capital Stock (Details) - USD ($)		12 Months Ended			63 Months Ended
	Jan. 14, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2018	Feb. 02, 2017
Class of Stock [Line Items]
Common stock cash dividends paid		$ 138,000,000	$ 110,000,000	$ 82,000,000
Dividends, share-based compensation		$ 1,000,000
Cash dividends declared per common share (in dollars per share)		$ 0.58	$ 0.44	$ 0.31
Payments for repurchase of common stock		$ 220,000,000	$ 400,000,000	$ 500,000,000	$ 1,534,000,000
Aggregate common stock repurchased (in shares)					52,905,959
Average cost of aggregate common stock repurchased (in dollars per share)					$ 28.99
Common Stock
Class of Stock [Line Items]
Common stock cash dividends paid		$ 138,000,000	$ 110,000,000	$ 82,000,000
Stock repurchase program, authorized amount						$ 2,100,000,000.0
Common stock repurchased (in shares)		8,936,302
Average cost of common stock repurchased (in dollars per share)		$ 24.62
Payments for repurchase of common stock		$ 220,000,000
Common Stock | Payments for Share Repurchases Related to Employee Stock Based Compensation
Class of Stock [Line Items]
Common stock repurchased (in shares)		0
Common Stock | Subsequent Event
Class of Stock [Line Items]
Cash dividends declared per common share (in dollars per share)	$ 0.16
Dividends declared on common stock	$ 37,000,000