Liquidity Facilities and Other Financing Arrangements (Details) - USD ($) $ in Thousands			12 Months Ended
	Sep. 25, 2019	Feb. 10, 2012	Dec. 31, 2021	Dec. 31, 2020	Aug. 02, 2019	Oct. 10, 2017
Short-term Debt [Line Items]
Short-term debt			$ 140,000	$ 373,800
Line of Credit Facility, Maximum Borrowing Capacity			1,300,000
Line of Credit Facility, Expiration Period	1 year
Working Capital Needs
Short-term Debt [Line Items]
Current borrowing capacity of line of credit						$ 800,000
Subsidiaries [Member]
Short-term Debt [Line Items]
Short-term debt			$ 140,000	$ 373,800
Weighted-average interest rate on short-term debt (percent)			1.60%	2.00%
Line of Credit Facility, Current Same-Day Borrowing Capacity			$ 75,000
Line of Credit Facility, Maximum Borrowing Capacity			$ 1,400,000		$ 1,000,000
Maximum capitalization percentage			65.00%
Derivative, Basis Spread on Variable Rate			1.25%
Line of Credit, Unused Capacity, Commitment Fee Percentage			0.175%
Line of Credit Facility, Expiration Period	1 year
Letters of Credit Outstanding, Amount			$ 0
Promissory Note Outstanding, Amount			0
Subsidiaries [Member] | Working Capital Needs
Short-term Debt [Line Items]
Current borrowing capacity of line of credit						$ 800,000
Subsidiaries [Member] | Letter of Credit | Working Capital Needs
Short-term Debt [Line Items]
Current borrowing capacity of line of credit			2,500
Subsidiaries [Member] | Line of Credit [Member] | Promissory Note with Puget Energy
Short-term Debt [Line Items]
Current borrowing capacity of line of credit			$ 30,000
Basis spread on variable rate (percent)			25.00%
Debt instrument variable rate basis			one-month LIBOR
Parent
Short-term Debt [Line Items]
Short-term debt			$ 0	$ 0
Revolving Credit Facility [Member]
Short-term Debt [Line Items]
Basis spread on variable rate (percent)			1.75%
Line of Credit Facility, Commitment Fee Percentage		0.275%
Line of Credit Facility, Fair Value of Amount Outstanding			$ 33,300
Revolving Credit Facility [Member] | Subsidiaries [Member]
Short-term Debt [Line Items]
Line of Credit Facility, Fair Value of Amount Outstanding			$ 0