Risk Management, Derivative Instruments and Hedging Activities - Statements of Operations Presentation (Details) - USD ($) $ in Millions	1 Months Ended	2 Months Ended	3 Months Ended	5 Months Ended	6 Months Ended
	Jun. 30, 2023	May 17, 2023	Jun. 30, 2024	May 17, 2023	Jun. 30, 2024
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Unrealized gain (loss) on commodity contracts	$ 41	$ (94)	$ 91	$ (63)	$ (44)
Realized and unrealized gain (loss) on interest rate contracts	124	(21)	100	732	157
Interest rate derivatives
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Realized and unrealized gain (loss) on interest rate contracts	1	0	1	0	9
Energy Revenues
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Realized gain (loss) on commodity contracts	70	65	38	644	196
Fuel and Energy Purchases
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Realized gain (loss) on commodity contracts	(20)	(13)	(8)	(34)	(7)
Operating Revenues
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Unrealized gain (loss) on commodity contracts	87	(85)	76	60	(32)
Energy Expenses
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Unrealized gain (loss) on commodity contracts	$ (46)	$ (9)	$ 15	$ (123)	$ (12)