Income Taxes (Income Tax (Provision) Benefit Attributable To Income From Continuing Operations) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Current:
U.S. federal	$ 12	$ 8	$ 0
U.S. state	(3)	(3)	(2)
Current income tax (provision) benefit	9	5	(2)
Deferred:
U.S. federal	55	(228)	(258)
U.S. state	(3)	(12)	(16)
Deferred income tax benefit	52	(240)	(274)
Income tax benefit (provision)	$ 61	$ (235)	$ (276)