Derivative Instruments and Hedging Activities - Schedule of Net Notional Volume Buy/(Sell) of the Company’s Open Derivative Transactions Broken Out by Commodity (Details) $ in Millions	9 Months Ended	12 Months Ended
Sep. 30, 2026 USD ($) BTU MWh	Dec. 31, 2025 USD ($) BTU MWh
Long \| Interest
Derivatives, Fair Value [Line Items]
Derivative, notional amount \| $	$ 4,888	$ 4,080
Heat Rate Call Option Commodity Contracts \| Short \| Power
Derivatives, Fair Value [Line Items]
Derivative nonmonetary notional amount (energy measure) \| MWh	20	29
Heat Rate Call Option Commodity Contracts \| Short \| Natural Gas
Derivatives, Fair Value [Line Items]
Derivative nonmonetary notional amount (energy measure) \| BTU	9	5

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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