Income Taxes (Schedule Of Income Tax Expense (Benefit) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Current income tax benefit:
United States federal, current income tax expense (benefit)	$ (219)	$ (3)	$ (14)
Various states, current income tax expense (benefit)		(2)	(3)
Total current income tax benefit	(219)	(5)	(17)
Deferred income tax expense (benefit):
United States federal, deferred income tax expense (benefit)	(304)	8	184
Various states, deferred income tax expense (benefit)	(24)	(33)	63
Total deferred income tax expense (benefit)	(328)	(25)	247
Total income tax expense (benefit)	$ (547)	$ (30)	$ 230