Summary of Consolidation and Significant Accounting Policy (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2021 USD ($) mi²	Mar. 31, 2020 USD ($)	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)
Summary of Consolidation Policy
Allowance for Credit Losses, Beginning Balance			$ 20,080	$ 8,294
Provision for Credit Loss	$ 12,452	$ 4,894
Receivables Charged-Off	(2,140)	(3,374)
Allowance for Credit Loss, Ending Balance	$ 30,392	9,814
Subsidiaries [Member]
Summary of Consolidation Policy
Area of Service Territory (in sqmi) | mi²	6,000
Variable Interest Entity [Line Items]
Contract Length, PPA	20 years
Variable Interest Entity, Measure of Activity, Expense	$ 5,700
Variable Interest Entity, Payable	$ 3,600
Subsidiaries [Member] | Tacoma LNG [Member]
Summary of Consolidation Policy
Jointly Owned Non-Utility Plant Share	43.00%
Construction in Progress, Gross	$ 216,500		207,700
Puget LNG [Member]
Summary of Consolidation Policy
Jointly Owned Non-Utility Plant Share	57.00%
Construction in Progress, Gross	$ 239,400		$ 231,600
Puget LNG [Member]
Summary of Consolidation Policy
Operating Costs and Expenses	$ 200	$ 300