Fair Value of Financial Assets and Liabilities - Consideration of Credit Risk and Concentrations (Details) $ in Millions		3 Months Ended
		Mar. 31, 2024 USD ($) Counterparty	Mar. 31, 2023 USD ($)
Consideration of Credit Risk and Concentrations [Abstract]
Derivative instruments designated as fair value hedges		$ 0	$ 0
Other Derivative Instruments
Consideration of Credit Risk and Concentrations [Abstract]
Pre-tax (gains) losses reclassified into income during the period from regulatory assets and (liabilities)		0	(9)
Pre-tax gains (losses) recognized during the period in income		(16)	(12)
Natural Gas Commodity | Other Derivative Instruments
Consideration of Credit Risk and Concentrations [Abstract]
Pre-tax (gains) losses reclassified into income during the period from regulatory assets and (liabilities)	[1]	0	9
Pre-tax gains (losses) recognized during the period in income	[1],[2]	(8)	$ (12)
Commodity Trading | Other Derivative Instruments
Consideration of Credit Risk and Concentrations [Abstract]
Pre-tax (gains) losses reclassified into income during the period from regulatory assets and (liabilities)		0
Pre-tax gains (losses) recognized during the period in income	[3]	$ (8)
Credit Concentration Risk
Consideration of Credit Risk and Concentrations [Abstract]
Number of most significant counterparties for wholesale, trading and non-trading commodity activities with credit exposure | Counterparty		10
Credit Concentration Risk | Municipal or Cooperative Entities or Other Utilities [Member]
Consideration of Credit Risk and Concentrations [Abstract]
Number of most significant counterparties for wholesale, trading and non-trading commodity activities with credit exposure | Counterparty		8
Credit Concentration Risk | External Credit Rating, Investment Grade [Member]
Consideration of Credit Risk and Concentrations [Abstract]
Number of most significant counterparties for wholesale, trading and non-trading commodity activities with credit exposure | Counterparty		4
Wholesale, trading and non-trading commodity credit exposure for the most significant counterparties		$ 25
Percentage of wholesale, trading and non-trading commodity credit exposure for the most significant counterparties (in hundredths)		39.00%
Credit Concentration Risk | External Credit Rating, Non Investment Grade [Member]
Consideration of Credit Risk and Concentrations [Abstract]
Number of most significant counterparties for wholesale, trading and non-trading commodity activities with credit exposure | Counterparty		0
Credit Concentration Risk | Internal Investment Grade
Consideration of Credit Risk and Concentrations [Abstract]
Number of most significant counterparties for wholesale, trading and non-trading commodity activities with credit exposure | Counterparty		6
Wholesale, trading and non-trading commodity credit exposure for the most significant counterparties		$ 25
Percentage of wholesale, trading and non-trading commodity credit exposure for the most significant counterparties (in hundredths)		40.00%

[1] Other than $2 million of 2024 losses recorded to electric fuel and purchased power, amounts are recorded to cost of natural gas sold and transported. Amounts are subject to cost-recovery mechanisms and reclassified out of income to a regulatory asset, as appropriate.

[2] Relates primarily to option premium amortization.

[3] Recorded to electric revenues. Presented amounts do not reflect non-derivative transactions or margin sharing with customers.