Regulatory Assets and Liabilities, Regulatory Assets (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2021	Dec. 31, 2020
Regulatory Assets [Line Items]
Regulatory Asset, Current		$ 527	$ 411
Regulatory assets		718	924
Regulatory assets not currently earning a return		691	399
Pension and Retiree Medical Obligations
Regulatory Assets [Line Items]
Regulatory Asset, Current		24	26
Regulatory assets		301	364
Excess deferred taxes - TCJA
Regulatory Assets [Line Items]
Regulatory Asset, Current		10	10
Regulatory assets		113	122
Recoverable Deferred Taxes on AFUDC Recorded in Plant
Regulatory Assets [Line Items]
Regulatory Asset, Current		0	0
Regulatory assets		114	113
Benson purchase power agreement termination and asset purchase
Regulatory Assets [Line Items]
Regulatory Asset, Current		10	10
Regulatory assets		$ 55	65
Regulatory Asset, Amortization Period		8 years
PI extended power update
Regulatory Assets [Line Items]
Regulatory Asset, Current		$ 4	3
Regulatory assets		$ 46	49
Regulatory Asset, Amortization Period		13 years
Contract Valuation Adjustments
Regulatory Assets [Line Items]
Regulatory Asset, Current	[1]	$ 18	16
Regulatory assets	[1]	34	48
Laurentian biomass PPA termination
Regulatory Assets [Line Items]
Regulatory Asset, Current		18	18
Regulatory assets		$ 18	36
Regulatory Asset, Amortization Period		2 years
Purchased Power Agreements
Regulatory Assets [Line Items]
Regulatory Asset, Current		$ 6	4
Regulatory assets		27	32
Sales True-Up and Revenue Decoupling
Regulatory Assets [Line Items]
Regulatory Asset, Current		33	101
Regulatory assets		$ 56	28
Sales True-Up and Revenue Decoupling | Minimum [Member]
Regulatory Assets [Line Items]
Regulatory Asset, Amortization Period		1 year
Sales True-Up and Revenue Decoupling | Maximum [Member]
Regulatory Assets [Line Items]
Regulatory Asset, Amortization Period		2 years
Conservation Programs
Regulatory Assets [Line Items]
Regulatory Asset, Current	[2]	$ 7	14
Regulatory assets	[2]	$ 22	23
Conservation Programs | Minimum [Member]
Regulatory Assets [Line Items]
Regulatory Asset, Amortization Period		1 year
Conservation Programs | Maximum [Member]
Regulatory Assets [Line Items]
Regulatory Asset, Amortization Period		2 years
Deferred Purchased Natural Gas and Electric Energy Costs
Regulatory Assets [Line Items]
Regulatory Asset, Current		$ 138	8
Regulatory assets		$ 190	18
Deferred Purchased Natural Gas and Electric Energy Costs | Minimum [Member]
Regulatory Assets [Line Items]
Regulatory Asset, Amortization Period		1 year
Deferred Purchased Natural Gas and Electric Energy Costs | Maximum [Member]
Regulatory Assets [Line Items]
Regulatory Asset, Amortization Period		5 years
Loss on Reacquired Debt
Regulatory Assets [Line Items]
Regulatory Asset, Current		$ 1	1
Regulatory assets		11	12
Nuclear Refueling Outage Costs
Regulatory Assets [Line Items]
Regulatory Asset, Current		37	28
Regulatory assets		$ 16	10
Nuclear Refueling Outage Costs | Minimum [Member]
Regulatory Assets [Line Items]
Regulatory Asset, Amortization Period		1 year
Nuclear Refueling Outage Costs | Maximum [Member]
Regulatory Assets [Line Items]
Regulatory Asset, Amortization Period		2 years
Environmental Remediation Costs
Regulatory Assets [Line Items]
Regulatory Asset, Current		$ 0	1
Regulatory assets		5	9
State Commission Adjustments
Regulatory Assets [Line Items]
Regulatory Asset, Current		0	0
Regulatory assets		3	3
Renewable Resources and Environmental Initiatives
Regulatory Assets [Line Items]
Regulatory Asset, Current		170	129
Regulatory assets		$ 3	1
Renewable Resources and Environmental Initiatives | Minimum [Member]
Regulatory Assets [Line Items]
Regulatory Asset, Amortization Period		1 year
Renewable Resources and Environmental Initiatives | Maximum [Member]
Regulatory Assets [Line Items]
Regulatory Asset, Amortization Period		2 years
Gas Pipeline Inspection and Remediation Costs
Regulatory Assets [Line Items]
Regulatory Asset, Current		$ 33	26
Regulatory assets		$ 0	0
Gas Pipeline Inspection and Remediation Costs | Minimum [Member]
Regulatory Assets [Line Items]
Regulatory Asset, Amortization Period		1 year
Gas Pipeline Inspection and Remediation Costs | Maximum [Member]
Regulatory Assets [Line Items]
Regulatory Asset, Amortization Period		2 years
Net AROs
Regulatory Assets [Line Items]
Regulatory Asset, Current	[3]	$ 0	0
Regulatory assets	[3]	316	(32)
Other
Regulatory Assets [Line Items]
Regulatory Asset, Current		18	16
Regulatory assets		$ 20	$ 23

[1] Includes the fair value of certain long-term PPAs used to meet energy capacity requirements and valuation adjustments on natural gas commodity purchases.

[2] Includes costs for conservation programs, as well as incentives allowed in certain jurisdictions.

[3] Includes amounts recorded for future recovery of AROs, less amounts recovered through nuclear decommissioning accruals and gains from decommissioning investments.