Capital Stock (Details) - USD ($) $ / shares in Units, $ in Millions		12 Months Ended			75 Months Ended
	Jan. 14, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2019
Class of Stock [Line Items]
Common stock cash dividends paid		$ 148	$ 138	$ 110
Dividends, share-based compensation		$ 2	$ 1
Cash dividends declared per common share (in dollars per share)		$ 0.64	$ 0.58	$ 0.44
Common stock repurchased (in shares)					52,905,959
Average cost of aggregate common stock repurchased (in dollars per share)					$ 28.99
Payments for repurchase of common stock		$ 0	$ 220	$ 400	$ 1,534
Common Stock
Class of Stock [Line Items]
Common stock cash dividends paid		$ 148	$ 138	$ 110
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