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Amount of allowance for credit loss on accounts receivable, classified as current.

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Generally recurring costs associated with normal operations except for the portion of these expenses which can be clearly related to production and included in cost of sales or services. Excludes Selling, General and Administrative Expense.

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Percentage of public utility's approved rate increase (decrease) by regulatory agency.

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Composite depreciation rate for public utility plants in service.

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Summary of Significant Accounting Policies (Details) $ in Thousands			12 Months Ended
	Dec. 19, 2017	Dec. 18, 2017	Dec. 31, 2019 USD ($) mi²	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Jan. 01, 2018 USD ($)	Jan. 01, 2017 USD ($)
Accounting Policies
Excise taxes collected			$ 236,500	$ 239,300	$ 257,100
Allowance for doubtful accounts			8,294	8,408
Monetized production tax credits			$ 67,500	$ 84,000
Electric Transmission
Accounting Policies
Annual depreciation provision			3.40%	3.30%	2.80%
Gas Transmission Equipment
Accounting Policies
Annual depreciation provision			2.80%	2.80%	3.40%
Common Plant
Accounting Policies
Annual depreciation provision			7.30%	7.10%	8.30%
Subsidiaries [Member]
Accounting Policies
Area of service territory (sqmi) \| mi²			6,000
Allowance for doubtful accounts			$ 8,294	$ 8,408
Public Utilities, Rate Case, Deferred Storm Costs Threshold						$ 10,000	$ 8,000
Puget LNG [Member]
Accounting Policies
Jointly Owned Non-Utility Plant Share			57.00%
Construction in Progress, Gross			$ 199,900	165,600
Operating Costs and Expenses			$ 1,200	2,000	$ 300
Tacoma LNG [Member]
Accounting Policies
Jointly Owned Non-Utility Plant Share			43.00%
Construction in Progress, Gross			$ 162,800	$ 130,800
Decoupling Mechanism [Member] \| Electricity, US Regulated [Member] \| Subsidiaries [Member] \| Maximum
Accounting Policies
Public Utilities, Approved Rate Increase (Decrease), Percentage	3.00%
Decoupling Mechanism [Member] \| Natural Gas, US Regulated [Member] \| Subsidiaries [Member] \| Maximum
Accounting Policies
Public Utilities, Approved Rate Increase (Decrease), Percentage	5.00%	3.00%