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		9 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2025	Sep. 30, 2024
Derivative Instruments, Gain (Loss) [Line Items]
Unrealized net gain (loss) from changes in fair value on derivative instruments:	$ 741	$ 766	$ 865	$ 1,317
Total unrealized net gain (loss) from change in fair value on derivative instruments	(567)	1,005	(1,316)	382
Net gain (loss) on derivative instruments	174	1,771	(451)	1,699
Interest Rate Swaps
Derivative Instruments, Gain (Loss) [Line Items]
Unrealized net gain (loss) from changes in fair value on derivative instruments:	(5)	(11)	(16)	(33)
Total unrealized net gain (loss) from change in fair value on derivative instruments	(5)	(73)	(68)	7
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:	735	754	878	1,172
Total unrealized net gain (loss) from change in fair value on derivative instruments	(573)	1,206	(1,179)	399
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:	11	23	3	178
Total unrealized net gain (loss) from change in fair value on derivative instruments	$ 11	$ (128)	$ (69)	$ (24)