Document And Entity Information	12 Months Ended
	Dec. 31, 2018 shares	Jun. 30, 2016 USD ($)
Entity Information [Line Items]
EBITDA to Interest Expense Denominator	1.0
Dividends, Earnings Before Interest, Tax, Deprecation and Amortization Ratio at Period End	1.0
Entity Registrant Name	PUGET ENERGY INC /WA
Entity Central Index Key	0001085392
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Filer Category	Non-accelerated Filer
Entity Public Float | $		$ 0
Entity Common Stock, Shares Outstanding | shares	200
Document Fiscal Year Focus	2018
Document Fiscal Period Focus	FY
Document Type	10-K
Amendment Flag	false
Entity Emerging Growth Company	false
Entity Small Business	false
Entity Shell Company	false
Document Period End Date	Dec. 31, 2018
Subsidiaries [Member]
Entity Information [Line Items]
EBITDA to Interest Expense Denominator	1.0
Dividends, Earnings Before Interest, Tax, Deprecation and Amortization Ratio at Period End	1.0
Entity Registrant Name	PUGET SOUND ENERGY INC
Entity Central Index Key	0000081100
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Filer Category	Non-accelerated Filer
Entity Public Float | $		$ 0
Entity Common Stock, Shares Outstanding | shares	85,903,791
Document Fiscal Year Focus	2018
Document Fiscal Period Focus	FY
Document Type	10-K
Amendment Flag	false
Entity Emerging Growth Company	false
Entity Small Business	false
Entity Shell Company	false
Document Period End Date	Dec. 31, 2018