Qualifying Cash Flow Hedges (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Financial Impact of Qualifying Cash Flow Hedges on Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Accumulated Other Comprehensive Income (Loss), Cumulative Changes in Net Gain (Loss) from Cash Flow Hedges, Effect Net of Tax, Beginning Balance	$ (23)	$ (24)	$ (26)
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI on Derivatives, Net of Tax	2	1	2
Accumulated Other Comprehensive Income (Loss), Cumulative Changes in Net Gain (Loss) from Cash Flow Hedges, Effect Net of Tax, Ending Balance	(21)	(23)	(24)
Impact of Derivative Activity [Abstract]
Fair Value Hedges, Net	0	0	0
Not Designated as Hedging Instrument
Impact of Derivative Activity [Abstract]
Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Derivatives Arising During Period, before Tax	0	0	0
Derivative Instruments Gain (Loss) Reclassified To Regulatory Assets And Liabilities Net	(1)	(10)	(5)
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net	0	0	0
Pre-tax gains (losses) reclassified into income during the period from regulatory assets and (liabilities)	(4)	(8)	1
Derivative, Gain (Loss) on Derivative, Net	(3)	(5)	(1)
Not Designated as Hedging Instrument | Commodity Trading Contract
Impact of Derivative Activity [Abstract]
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net	0	0	0
Pre-tax gains (losses) reclassified into income during the period from regulatory assets and (liabilities)	0	0	0
Derivative, Gain (Loss) on Derivative, Net	12	3	3	[1]
Not Designated as Hedging Instrument | Natural Gas Commodity Contract
Impact of Derivative Activity [Abstract]
Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Derivatives Arising During Period, before Tax	0	0	0
Derivative Instruments Gain (Loss) Reclassified To Regulatory Assets And Liabilities Net	(1)	(10)	(5)
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net	0	0	0
Pre-tax gains (losses) reclassified into income during the period from regulatory assets and (liabilities)	(4)	(8)	(1)
Derivative, Gain (Loss) on Derivative, Net	(15)	(8)	(4)
Designated as Hedging Instrument | Cash Flow Hedges
Impact of Derivative Activity [Abstract]
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net	(2)	(1)	(2)
Pre-tax gains (losses) reclassified into income during the period from regulatory assets and (liabilities)	0	0	0
Derivative, Gain (Loss) on Derivative, Net	0	0	0
Designated as Hedging Instrument | Cash Flow Hedges | Interest Rate Contract
Impact of Derivative Activity [Abstract]
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net	(2)	(1)	(2)	[2]
Pre-tax gains (losses) reclassified into income during the period from regulatory assets and (liabilities)	0	0	0
Derivative, Gain (Loss) on Derivative, Net	$ 0	$ 0	$ 0

[1] Recorded to electric operating revenues. Portions of these gains and losses are subject to sharing with electric customers through margin-sharing mechanisms and deducted from gross revenue, as appropriate.

[2] Recorded to interest charges.