Earnings Per Share (Reconciliation of the Numerators and Denominators of the Basic and Diluted Per Shares) (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Net Income (Loss) Available to Common Stockholders, Basic [Abstract]
Net income (numerator for basic and diluted calculations)	$ 213	$ 263	$ 283	$ 635
Shares:
Weighted average outstanding shares (denominator for basic calculation)	68	63	65	63
Equivalent shares from outstanding stock options	0	1	0	1
Denominator for diluted calculation	68	64	65	64
Earnings Per Share:
Basic earnings per share	$ 3.13	$ 4.19	$ 4.39	$ 10.13
Diluted earnings per share	$ 3.12	$ 4.12	$ 4.36	$ 9.93