Income Taxes - PAC - Components of Income Tax Expense (Benefit) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Current:
Federal	$ (1,701)	$ (1,537)	$ (956)
State	(177)	(121)	(13)
Total current	(1,778)	(1,572)	(888)
Deferred:
Federal	1,037	1,438	431
State	(476)	424	(127)
Total deferred	650	1,883	296
Investment tax credits	(4)	(3)	(6)
Total	(1,132)	308	(598)
PAC
Current:
Federal	(150)	19	158
State	7	30	34
Total current	(143)	49	192
Deferred:
Federal	26	(124)	(132)
State	40	1	4
Total deferred	66	(123)	(128)
Investment tax credits	(2)	(1)	(3)
Total	$ (79)	$ (75)	$ 61