SCHEDULE I CONDENSED FINANCIAL INFORMATION OF PUGET ENERGY Notes (Details) - USD ($)	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Net Income (Loss) Attributable to Parent									$ 210,708,000	$ 235,622,000	$ 175,194,000
Comprehensive Income (Loss), Net of Tax, Attributable to Parent									203,761,000	182,702,000	184,624,000
Net Cash Provided by (Used in) Operating Activities									527,336,000	904,181,000	972,131,000
Net Cash Provided by (Used in) Investing Activities									(952,479,000)	(1,070,573,000)	(1,040,330,000)
Parent Company [Member]
Net Income (Loss) Attributable to Parent	$ 150,949,000	$ (39,443,000)	$ (32,952,000)	$ 132,154,000	$ 107,053,000	$ (21,970,000)	$ 3,642,000	$ 146,897,000	210,708,000	235,622,000	175,194,000
Comprehensive Income (Loss), Net of Tax, Attributable to Parent									203,761,000	182,702,000	184,624,000
Net Cash Provided by (Used in) Operating Activities									68,724,000	79,176,000	139,005,000
Net Cash Provided by (Used in) Investing Activities									(251,708,000)	(59,864,000)	(102,814,000)
Subsidiaries [Member]
Net Income (Loss) Attributable to Parent	$ 169,204,000	$ (15,257,000)	$ (8,325,000)	$ 147,302,000	$ 123,456,000	$ 3,891,000	$ 26,778,000	$ 163,037,000	292,924,000	317,162,000	320,054,000
Comprehensive Income (Loss), Net of Tax, Attributable to Parent									295,331,000	253,184,000	338,659,000
Net Cash Provided by (Used in) Operating Activities									623,924,000	995,904,000	1,086,803,000
Net Cash Provided by (Used in) Investing Activities									$ (912,363,000)	$ (1,008,409,000)	$ (963,411,000)