Net Income Per Share (Basic And Diluted Net Income Per Share) (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Earnings Per Share [Abstract]
Net income	$ 292	$ 318	$ 929	$ 925
Income allocated to participating securities	2	2	5	6
Net income attributable to shares	$ 290	$ 316	$ 924	$ 919
Basic average shares	147	167	152	170
Basic net income per share	$ 1.98	$ 1.89	$ 6.08	$ 5.41
Basic average shares	147	167	152	170
Net effect of the assumed exercise of stock options	1	2	2	2
Net effect of the assumed exercise of warrants	0	1	0	1
Diluted average shares	148	170	154	173
Diluted net income per share	$ 1.96	$ 1.86	$ 6.02	$ 5.32