Capital Stock (Details) - USD ($)		3 Months Ended		63 Months Ended
	Apr. 09, 2018	Mar. 31, 2018	Mar. 31, 2017	Mar. 31, 2018	Feb. 02, 2017
Class of Stock [Line Items]
Cash dividends paid		$ 34,000,000	$ 25,000,000
Cash dividends declared (dollars per share)		$ 0.14	$ 0.10
Payments for repurchase of stock		$ 25,000,000	$ 25,000,000
Common Stock
Class of Stock [Line Items]
Cash dividends paid		$ 34,000,000
Stock repurchase program, authorized amount					$ 2,100,000,000.0
Shares repurchased (shares)		874,678		44,844,335
Average price of shares repurchased (dollars per share)		$ 28.58		$ 29.85
Payments for repurchase of stock		$ 25,000,000		$ 1,338,000,000
Common Stock | Payments for Share Repurchases Related to Employee Stock Based Compensation
Class of Stock [Line Items]
Shares repurchased (shares)		0
Common Stock | Subsequent Event
Class of Stock [Line Items]
Cash dividends declared (dollars per share)	$ 0.14
Cash dividends declared	$ 34,000,000