Capital Stock (Details) - USD ($)		12 Months Ended			52 Months Ended
	Jan. 16, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2017	Feb. 02, 2017
Class of Stock [Line Items]
Common stock cash dividends paid		$ 110,000,000	$ 82,000,000	$ 68,000,000
Cash dividends declared per common share (in dollars per share)		$ 0.44	$ 0.31	$ 0.25
Payments for repurchase of common stock		$ 400,000,000	$ 500,000,000	$ 180,000,000	$ 1,313,000,000
Aggregate common stock repurchased (in shares)					43,969,657
Average cost of aggregate common stock repurchased (in dollars per share)					$ 29.87
Common Stock
Class of Stock [Line Items]
Common stock cash dividends paid		$ 110,000,000	$ 82,000,000	$ 68,000,000
Stock repurchase program, authorized amount						$ 2,100,000,000.0
Common stock repurchased (in shares)		12,755,547
Average cost of common stock repurchased (in dollars per share)		$ 31.37
Payments for repurchase of common stock		$ 400,000,000
Subsequent Event | Common Stock
Class of Stock [Line Items]
Cash dividends declared per common share (in dollars per share)	$ 0.14
Dividends declared on common stock	$ 34,000,000
Payments for Share Repurchases Related to Employee Stock Based Compensation | Common Stock
Class of Stock [Line Items]
Common stock repurchased (in shares)		0