Capital Stock (Narrative) (Details) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2019	Apr. 30, 2019	Dec. 31, 2018	Oct. 05, 2016
Class of Stock [Line Items]
Incremental increase to authorized amount of share repurchase program		$ 250
Authorized amount of share repurchase program		$ 1,050
Warrants issued (in shares)	1,845,568
Common stock, par value (in dollars per share)	$ 0.01		$ 0.01
Percentage of common stock in transaction	90.00%
Warrants, repurchase amount (in dollars per share)	$ 0
Warrants exercised (in shares)	386
Common Class A
Class of Stock [Line Items]
Warrants issued (in shares)				1,914,856
Common stock, par value (in dollars per share)				$ 0.01
Warrant exercise price (in dollars per share)				$ 57.00