Summary of Significant Accounting Policies and Other Matters - Reconciliation of Cash, Temporary Investments and Restricted Cash (Details) $ in Millions	Jun. 30, 2025 USD ($) MWh	Dec. 31, 2024 USD ($)	Jun. 30, 2024 USD ($) MWh	Mar. 01, 2023 MWh
Cash and Cash Equivalents [Line Items]
Cash and temporary cash investments	$ 1,506	$ 1,324	$ 1,500
Restricted cash	1		7
Total cash, temporary cash investments and restricted cash	$ 1,507		$ 1,507
Electric Energy (MWh)
Cash and Cash Equivalents [Line Items]
Notional amount | MWh	30,092,325
Broken Bow II | Electric Energy (MWh) | Clean Energy Businesses
Cash and Cash Equivalents [Line Items]
Notional amount | MWh			75	75