Earnings Per Share (Reconciliation of the Numerators and Denominators of the Basic and Diluted Per Shares) (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Net Income (Loss) Available to Common Stockholders, Basic [Abstract]
Net income (numerator for basic and diluted calculations)	$ (88)	$ 170
Shares:
Weighted Average Number of Shares Outstanding, Basic	62,000,000	63,000,000
Incremental Common Shares Attributable to Dilutive Effect of Share-based Payment Arrangements	1,000,000	1,000,000
Denominator for diluted calculation	63,000,000	64,000,000
Earnings Per Share:
Basic earnings per share	$ (1.41)	$ 2.70
Diluted earnings per share	$ (1.41)	$ 2.65