Net Income Per Common Share (Basic And Diluted Net Income Per Share) (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended			6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020		Jun. 30, 2021	Jun. 30, 2020
Earnings Per Share [Abstract]
Net income	$ 328	$ 118	[1]	$ 678	$ 59	[1]
Income allocated to participating securities	2	1		3	1
Preferred stock dividends	5	0		11	0
Net income attributable to common shares	$ 321	$ 117		$ 664	$ 58
Basic average common shares	136.0	139.0		138.0	140.0
Basic net income per common share	$ 2.35	$ 0.85		$ 4.81	$ 0.42
Basic average common shares	136.0	139.0		138.0	140.0
Net effect of the assumed exercise of stock options	2.0	0.0		2.0	1.0
Diluted average common shares	138.0	139.0		140.0	141.0
Diluted net income per common share	$ 2.32	$ 0.84		$ 4.76	$ 0.42

[1] See Defined Benefit Pension and Other Postretirement Costs in Note 1.