Derivatives - Schedule of Pretax Effect on Net Income of Derivatives Not Under Hedge Accounting, Including Realized and Unrealized Effects (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2025	Jun. 30, 2024	Jun. 30, 2025	Jun. 30, 2024
Derivative Instruments, Gain (Loss) [Line Items]
Unrealized net gain (loss) from changes in fair value on derivative instruments:	$ (60)	$ 175	$ 124	$ 551
Total unrealized net gain (loss) from change in fair value on derivative instruments	50	(118)	(749)	(623)
Net gain (loss) on derivative instruments	(10)	57	(625)	(72)
Interest Rate Swaps
Derivative Instruments, Gain (Loss) [Line Items]
Unrealized net gain (loss) from changes in fair value on derivative instruments:	(6)	(11)	(11)	(22)
Total unrealized net gain (loss) from change in fair value on derivative instruments	(20)	22	(63)	80
Commodity contracts unrealized (gain) loss in operating revenues | Commodity Contracts
Derivative Instruments, Gain (Loss) [Line Items]
Unrealized net gain (loss) from changes in fair value on derivative instruments:	(69)	157	143	418
Total unrealized net gain (loss) from change in fair value on derivative instruments	119	(199)	(606)	(807)
Commodity contracts unrealized gain (loss) in fuel, purchased power costs, and delivery fees | Commodity Contracts
Derivative Instruments, Gain (Loss) [Line Items]
Unrealized net gain (loss) from changes in fair value on derivative instruments:	15	29	(8)	155
Total unrealized net gain (loss) from change in fair value on derivative instruments	$ (49)	$ 59	$ (80)	$ 104