Regulation and Rates Net regulatory assets and liabilities (Details) - USD ($)	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Jan. 01, 2018
Regulatory Assets [Line Items]
Regulatory Assets	$ 904,342,000	$ 962,228,000
Regulatory Liabilities	2,025,500,000	1,791,094,000
Accrual for Environmental Loss Contingencies	61,500,000
Deferred income tax charge
Regulatory Assets [Line Items]
Regulatory Liabilities	$ 563,000	565,000
Regulatory liabilities related to power contracts
Regulatory Assets [Line Items]
Net Regulatory Assets, Remaining Amortization Period, Max	30 years
Net Regulatory Assets, Remaining Amortization Period, Min	3 years
Regulatory Liabilities	$ 63,660,000	80,934,000
Various other regulatory liabilities
Regulatory Assets [Line Items]
Regulatory Liabilities	1,264,000	1,264,000
Net Regulatory Asset (Liability)
Regulatory Assets [Line Items]
Net Regulatory Assets	(1,121,158,000)	(828,866,000)
Requlatory Assets Related to Power Contracts
Regulatory Assets [Line Items]
Regulatory Assets	$ 7,904,000	9,689,000
Net Regulatory Assets, Remaining Amortization Period, Max	30 years
Net Regulatory Assets, Remaining Amortization Period, Min	3 years
Subsidiaries [Member]
Regulatory Assets [Line Items]
Regulatory Assets	$ 896,438,000	952,539,000
Regulatory Asset, Amortization Period	1 year
Regulatory Liability, Amortization Period	1 year
Regulatory Liabilities	$ 1,961,139,000	1,709,461,000
Regulatory Liabilities Reclassified from Accumulated Depreciation	639,300,000	563,100,000
Storm Damage Costs Incurred During Period	32,200,000	51,400,000
Public Utilities, Rate Case, Deferred Storm Costs Threshold			$ 10,000,000
Public Utilities, Rate Case, Deferred Storm Qualifying Costs			$ 500,000
Subsidiaries [Member] | Deferred income tax charge
Regulatory Assets [Line Items]
Regulatory Liabilities	811,724,000	866,541,000
Subsidiaries [Member] | Repurposed production tax credits [Member]
Regulatory Assets [Line Items]
Regulatory Liabilities	$ 133,855,000	134,270,000
Subsidiaries [Member] | Deferred decoupling revenue, net [Member]
Regulatory Assets [Line Items]
Regulatory Liability, Amortization Period	2 years
Regulatory Liabilities	$ 63,206,000	36,506,000
Subsidiaries [Member] | Various other regulatory liabilities
Regulatory Assets [Line Items]
Regulatory Liabilities	5,583,000	35,093,000
Subsidiaries [Member] | Liabilities, Total
Regulatory Assets [Line Items]
Regulatory Liabilities	1,961,139,000	1,709,461,000
Subsidiaries [Member] | Green Direct
Regulatory Assets [Line Items]
Regulatory Liabilities	11,837,000	13,194,000
Subsidiaries [Member] | Net Regulatory Asset (Liability)
Regulatory Assets [Line Items]
Net Regulatory Assets	(1,064,701,000)	(756,922,000)
Subsidiaries [Member] | PGA Unrealized Gain
Regulatory Assets [Line Items]
Regulatory Liabilities	287,725,000	60,728,000
Subsidiaries [Member] | Removal Costs
Regulatory Assets [Line Items]
Regulatory Liabilities	$ 639,320,000	563,129,000
Subsidiaries [Member] | PGA Liability
Regulatory Assets [Line Items]
Regulatory Asset, Amortization Period	2 years
Regulatory Liabilities	$ 3,536,000	0
Subsidiaries [Member] | Refund on Counterparty Settlement
Regulatory Assets [Line Items]
Regulatory Asset, Amortization Period	1 year
Regulatory Liabilities	$ 4,353,000	0
Subsidiaries [Member] | Storm Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets	$ 127,524,000	127,789,000
Net Regulatory Assets, Remaining Amortization Period, Max	5 years
Net Regulatory Assets, Remaining Amortization Period, Min	3 years
Subsidiaries [Member] | Chelan PUD contract initiation
Regulatory Assets [Line Items]
Regulatory Assets	$ 62,611,000	69,699,000
Regulatory Asset, Amortization Period	8 years 9 months 18 days
Subsidiaries [Member] | Environmental remediation
Regulatory Assets [Line Items]
Regulatory Assets	$ 141,893,000	127,977,000
Subsidiaries [Member] | Lower Snake River
Regulatory Assets [Line Items]
Regulatory Assets	$ 48,536,000	53,757,000
Regulatory Asset, Amortization Period	14 years 4 months 24 days
Subsidiaries [Member] | Deferred decoupling revenue, net [Member]
Regulatory Assets [Line Items]
Regulatory Assets	$ 36,773,000	79,125,000
Regulatory Asset, Amortization Period	2 years
Subsidiaries [Member] | Baker Dam Licensing Operating Maintenance Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets	$ 55,049,000	54,525,000
Hydro license term	50 years
Subsidiaries [Member] | Deferred Washington Commission AFUDC
Regulatory Assets [Line Items]
Regulatory Assets	$ 61,463,000	62,244,000
Regulatory Asset, Amortization Period	30 years
Subsidiaries [Member] | Property tax tracker
Regulatory Assets [Line Items]
Regulatory Assets	$ 12,398,000	25,896,000
Regulatory Asset, Amortization Period	2 years
Subsidiaries [Member] | Unamortized loss on reacquired debt
Regulatory Assets [Line Items]
Regulatory Assets	$ 33,732,000	35,805,000
Net Regulatory Assets, Remaining Amortization Period, Max	45 years
Net Regulatory Assets, Remaining Amortization Period, Min	1 year
Subsidiaries [Member] | Energy Conservation Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets	$ 10,296,000	3,573,000
Subsidiaries [Member] | GTZ depreciation expense deferral [Member]
Regulatory Assets [Line Items]
Regulatory Assets	$ 49,605,000	50,220,000
Net Regulatory Assets, Remaining Amortization Period, Max	4 years
Net Regulatory Assets, Remaining Amortization Period, Min	1 year
Subsidiaries [Member] | Advanced metering infrastructure [Member]
Regulatory Assets [Line Items]
Regulatory Assets	$ 30,431,000	23,037,000
Regulatory Asset, Amortization Period	3 years
Subsidiaries [Member] | Generation plant major maintenance [Member]
Regulatory Assets [Line Items]
Regulatory Assets	$ 20,374,000	12,094,000
Net Regulatory Assets, Remaining Amortization Period, Max	7 years
Net Regulatory Assets, Remaining Amortization Period, Min	3 years
Subsidiaries [Member] | Mint Farm ownership and operating costs
Regulatory Assets [Line Items]
Regulatory Assets	$ 4,317,000	6,318,000
Regulatory Asset, Amortization Period	2 years 3 months 18 days
Subsidiaries [Member] | PGA receivable [Member]
Regulatory Assets [Line Items]
Regulatory Assets	$ 0	57,935,000
Regulatory Asset, Amortization Period	2 years
Subsidiaries [Member] | Snoqualmie Licensing Operating Maintenance Costs
Regulatory Assets [Line Items]
Regulatory Assets	$ 7,445,000	7,446,000
Hydro license term	40 years
Subsidiaries [Member] | Colstrip major maintenance [Member]
Regulatory Assets [Line Items]
Regulatory Assets	$ 4,035,000	4,035,000
Regulatory Asset, Amortization Period	3 years
Subsidiaries [Member] | PCA Mechanism [Member]
Regulatory Assets [Line Items]
Regulatory Assets	$ 112,207,000	79,546,000
Subsidiaries [Member] | WUTC Electric Vehicle
Regulatory Assets [Line Items]
Regulatory Assets	$ 7,796,000	6,109,000
Regulatory Asset, Amortization Period	4 years
Subsidiaries [Member] | WUTC COVID-19
Regulatory Assets [Line Items]
Regulatory Assets	$ 7,051,000	3,657,000
Subsidiaries [Member] | Low Income Program Costs
Regulatory Assets [Line Items]
Regulatory Assets	17,370,000	21,755,000
Subsidiaries [Member] | Various other regulatory assets
Regulatory Assets [Line Items]
Regulatory Assets	7,060,000	32,508,000
Subsidiaries [Member] | Water Heater Rental Property Loss
Regulatory Assets [Line Items]
Regulatory Assets	5,725,000	5,725,000
Subsidiaries [Member] | Regulatory Filing Fee Deferral
Regulatory Assets [Line Items]
Regulatory Assets	7,559,000	0
Subsidiaries [Member] | WUTC LNG
Regulatory Assets [Line Items]
Regulatory Assets	$ 25,188,000	$ 1,764,000