Derivatives - Schedule of Notional Amounts of Outstanding Derivative Positions (Details) gal in Millions, certificate in Millions, T in Millions, MMBTU in Millions, $ in Millions	6 Months Ended	12 Months Ended
	Jun. 30, 2025 USD ($) certificate MMBTU GWh T gal	Dec. 31, 2024 USD ($) certificate GWh MMBTU T gal
Natural gas
Derivatives, Fair Value [Line Items]
Derivative, nonmonetary notional amount, energy measure | MMBTU	4,403	4,568
Electricity
Derivatives, Fair Value [Line Items]
Derivative, nonmonetary notional amount, energy measure | GWh	878,570	796,982
Financial transmission rights / Congestion revenue rights
Derivatives, Fair Value [Line Items]
Derivative, nonmonetary notional amount, energy measure | GWh	282,049	248,742
Coal
Derivatives, Fair Value [Line Items]
Derivative, nonmonetary notional amount, mass | T	28	27
Fuel oil
Derivatives, Fair Value [Line Items]
Derivative, nonmonetary notional amount, volume | gal	4	2
Emissions
Derivatives, Fair Value [Line Items]
Derivative, nonmonetary notional amount, mass | T	31	28
Renewable energy certificates
Derivatives, Fair Value [Line Items]
Nonmonetary notional volume | certificate	30	31
Interest rate swaps – variable/fixed
Derivatives, Fair Value [Line Items]
Derivative, notional amount | $	$ 5,478	$ 5,300
Interest rate swaps – fixed/variable
Derivatives, Fair Value [Line Items]
Derivative, notional amount | $	$ 700	$ 700