Summary of Significant Accounting Policies and Other Matters - Reconciliation of Cash, Temporary Investments and Restricted Cash (Details) $ in Millions	Mar. 31, 2023 USD ($) MWh	Dec. 31, 2022 USD ($)	Mar. 31, 2022 USD ($)
Cash and Cash Equivalents [Line Items]
Cash and temporary cash investments	$ 771	$ 1,282	$ 108
Restricted cash	2		89
Total cash, temporary cash investments and restricted cash	$ 773		197
Electric Energy (MWh)
Cash and Cash Equivalents [Line Items]
Notional amount | MWh	30,093,325
Broken Bow II | Electric Energy (MWh) | Clean Energy Businesses
Cash and Cash Equivalents [Line Items]
Notional amount | MWh	75
Subsidiaries
Cash and Cash Equivalents [Line Items]
Cash and temporary cash investments	$ 36	$ 1,056	49
Restricted cash	0		4
Total cash, temporary cash investments and restricted cash	$ 36		53
Clean Energy Businesses | Cash Collateral Held for Project Finance Agreements
Cash and Cash Equivalents [Line Items]
Restricted cash			$ 85