Summary of Significant Accounting Policies and Other Matters - Reconciliation of Cash, Temporary Investments and Restricted Cash (Details) $ in Millions	Mar. 31, 2024 USD ($) MWh	Dec. 31, 2023 USD ($)	Mar. 31, 2023 USD ($)
Cash and Cash Equivalents [Line Items]
Cash and temporary cash investments	$ 169	$ 1,189	$ 771
Restricted cash	6		2
Total cash, temporary cash investments and restricted cash	$ 175		$ 773
Electric Energy (MWh)
Cash and Cash Equivalents [Line Items]
Notional amount | MWh	31,374,625
Broken Bow II | Electric Energy (MWh) | Clean Energy Businesses
Cash and Cash Equivalents [Line Items]
Notional amount | MWh	75