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, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Earnings Per Share [Abstract]
Net Income (Loss) Attributable to Parent	$ 235	$ 263	$ 202	$ 170	$ 110	$ 301	$ 205	$ 100	$ 870	$ 716	$ 1,822
Weighted Average Number of Shares Outstanding, Diluted [Abstract]
Weighted Average Number of Shares Outstanding, Basic									62,684	63,658	64,427
Equivalent shares from outstanding stock options									1,198	1,436	1,326
Weighted Average Number of Shares Outstanding, Diluted									63,882	65,094	65,753
Earnings per share
Earnings Per Share, Basic (in dollars per share)	$ 3.75	$ 4.19	$ 3.23	$ 2.70	$ 1.75	$ 4.76	$ 3.19	$ 1.55	$ 13.88	$ 11.25	$ 28.28
Earnings Per Share, Diluted (in dollars per share)	$ 3.68	$ 4.12	$ 3.18	$ 2.65	$ 1.72	$ 4.68	$ 3.13	$ 1.52	$ 13.62	$ 11.00	$ 27.71