Capital Stock (Details) - USD ($)		3 Months Ended		6 Months Ended		45 Months Ended
	Jul. 12, 2017	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Feb. 02, 2017
Class of Stock [Line Items]
Cash dividends paid				$ 50,000,000	$ 38,000,000
Cash dividends declared (dollars per share)		$ 0.10	$ 0.07	$ 0.20	$ 0.14
Payments for repurchase of stock				$ 30,000,000	$ 150,000,000
Common Stock
Class of Stock [Line Items]
Cash dividends paid				$ 50,000,000
Stock repurchase program, authorized amount							$ 2,100,000,000.0
Shares repurchased (shares)		146,626		843,120		32,057,230
Average price of shares repurchased (dollars per share)		$ 35.17		$ 35.77		$ 29.43
Payments for repurchase of stock		$ 5,000,000		$ 30,000,000		$ 943,000,000
Common Stock | Subsequent Event
Class of Stock [Line Items]
Cash dividends declared (dollars per share)	$ 0.10
Cash dividends declared	$ 25,000,000
Payments for Share Repurchases Related to Employee Stock Based Compensation | Common Stock
Class of Stock [Line Items]
Shares repurchased (shares)				0