Earnings Per Share (Schedule of Earnings Per Share Basic and Diluted) (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Earnings Per Share [Abstract]
Net Income (Loss) Attributable to Parent	$ 132	$ 213	$ 158	$ (88)	$ 235	$ 263	$ 202	$ 170	$ 415	$ 870	$ 716
Weighted Average Number of Shares Outstanding, Diluted [Abstract]
Weighted Average Number of Shares Outstanding, Basic									65,400	62,700	63,700
Equivalent shares from outstanding stock options									400	1,200	1,400
Weighted Average Number of Shares Outstanding, Diluted									65,800	63,900	65,100
Earnings per share
Earnings Per Share, Basic (in dollars per share)	$ 1.95	$ 3.13	$ 2.49	$ (1.41)	$ 3.75	$ 4.19	$ 3.23	$ 2.70	$ 6.35	$ 13.88	$ 11.25
Earnings Per Share, Diluted (in dollars per share)	$ 1.94	$ 3.12	$ 2.48	$ (1.41)	$ 3.68	$ 4.12	$ 3.18	$ 2.65	$ 6.31	$ 13.62	$ 11.00