Income Taxes (Details of Income Tax Expense for Continuing Operations Including Noncontrolling Interests) (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Current:
Federal	$ (52)	$ (139)	$ 0
State	(39)	3	34
Total current expense (benefit)	(91)	(136)	34
Deferred:
Taxes before operating loss carryforwards, investment tax credits and tax reform	61	158	(90)
Tax utilization expense of operating loss carryforwards	34	33	102
State	7	17	(57)
Total deferred expense (benefit)	102	208	(45)
Investment tax credit-amortization	(2)	(1)	(1)
Total income tax expense (benefit)	$ 9	$ 71	$ (12)