SCHEDULE I CONDENSED FINANCIAL INFORMATION OF PUGET ENERGY - Condensed Statements of Cash Flows (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Adjustments to reconcile net income to net cash provided by (used in) operating activities:
Net cash provided by (used in) operating activities	$ 904,181	$ 972,131	$ 729,290
Investing activities:
Other	2,097	(195)	(1,921)
Net cash provided by (used in) investing activities	(1,070,573)	(1,040,330)	(708,365)
Financing activities:
Dividends paid	(77,204)	(123,307)	(148,965)
Proceeds from long-term debt and bonds issued	804,050	90,120	12,481
Issuance/redemption of term-loan and other long-term debt	(600,000)	0	0
Net cash provided by (used in) financing activities	185,193	63,664	(30,072)
Net increase (decrease) in cash, cash equivalents, and restricted cash	18,801	(4,535)	(9,147)
Cash, cash equivalents, and restricted cash at end of period	37,521	26,616
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents	55,562	36,761	41,296	$ 50,443
Parent Company [Member]
Adjustments to reconcile net income to net cash provided by (used in) operating activities:
Net cash provided by (used in) operating activities	79,176	139,005	145,719
Investing activities:
Adjustments to Additional Paid in Capital, Other	0	(24,222)	0
(Increase) decrease in loan to subsidiary	(59,864)	(78,155)	0
Other	0	(437)	(6,078)
Net cash provided by (used in) investing activities	(59,864)	(102,814)	(6,078)
Financing activities:
Dividends paid	(77,204)	(123,307)	(148,965)
Proceeds from long-term debt and bonds issued	209,300	0	0
Issuance/redemption of term-loan and other long-term debt	(150,000)	90,120	12,480
Issue costs and others	(92)	(2,650)	(3,398)
Net cash provided by (used in) financing activities	(17,996)	(35,837)	(139,883)
Net increase (decrease) in cash, cash equivalents, and restricted cash	1,316	354	(242)
Cash, cash equivalents, and restricted cash at end of period	2,067	751
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents	$ 2,067	$ 751	$ 397	$ 639

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