Fair Value of Financial Assets and Liabilities - Fair Value Assets and Liabilities Measure on a Recurring Basis Gain Loss Included in Earnings (Details) - Level 3 - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2026	Mar. 31, 2025
Fair Value Assets and Liabilities Measured on a Recurring Basis Gain Loss Included in Earnings [Line Items]
Total (losses) gains included in net income	$ 850	$ (130)
Total unrealized (losses) gains	570	(95)
Operating revenues
Fair Value Assets and Liabilities Measured on a Recurring Basis Gain Loss Included in Earnings [Line Items]
Total (losses) gains included in net income	582	38
Total unrealized (losses) gains	528	(8)
Purchased power and fuel
Fair Value Assets and Liabilities Measured on a Recurring Basis Gain Loss Included in Earnings [Line Items]
Total (losses) gains included in net income	75	(169)
Total unrealized (losses) gains	40	(88)
Other, net
Fair Value Assets and Liabilities Measured on a Recurring Basis Gain Loss Included in Earnings [Line Items]
Total (losses) gains included in net income	2	1
Total unrealized (losses) gains	$ 2	$ 1