Fair Value Measurements Assets and Liabilities (Details) (USD $)	3 Months Ended				9 Months Ended				3 Months Ended				9 Months Ended				3 Months Ended				9 Months Ended
	Sep. 30, 2014		Sep. 30, 2013		Sep. 30, 2014		Sep. 30, 2013		Sep. 30, 2014 Electric portfolio [Member]		Sep. 30, 2013 Electric portfolio [Member]		Sep. 30, 2014 Electric portfolio [Member]		Sep. 30, 2013 Electric portfolio [Member]		Sep. 30, 2014 Natural gas portfolio [Member]		Sep. 30, 2013 Natural gas portfolio [Member]		Sep. 30, 2014 Natural gas portfolio [Member]		Sep. 30, 2013 Natural gas portfolio [Member]		Sep. 30, 2014 Commodity Contract [Member]	Dec. 31, 2013 Commodity Contract [Member]	Sep. 30, 2014 Interest Rate Contract [Member]		Dec. 31, 2013 Interest Rate Contract [Member]		Sep. 30, 2014 Fair Value, Measurements, Recurring [Member] Parent Company [Member] Level 2 [Member]	Dec. 31, 2013 Fair Value, Measurements, Recurring [Member] Parent Company [Member] Level 2 [Member]	Sep. 30, 2014 Fair Value, Measurements, Recurring [Member] Parent Company [Member] Level 2 [Member] Interest Rate Contract [Member]	Dec. 31, 2013 Fair Value, Measurements, Recurring [Member] Parent Company [Member] Level 2 [Member] Interest Rate Contract [Member]	Sep. 30, 2014 Fair Value, Measurements, Recurring [Member] Parent Company [Member] Level 3 [Member]	Dec. 31, 2013 Fair Value, Measurements, Recurring [Member] Parent Company [Member] Level 3 [Member]	Sep. 30, 2014 Fair Value, Measurements, Recurring [Member] Parent Company [Member] Level 3 [Member] Interest Rate Contract [Member]	Dec. 31, 2013 Fair Value, Measurements, Recurring [Member] Parent Company [Member] Level 3 [Member] Interest Rate Contract [Member]	Sep. 30, 2014 Fair Value, Measurements, Recurring [Member] Parent Company [Member] Total [Member]	Dec. 31, 2013 Fair Value, Measurements, Recurring [Member] Parent Company [Member] Total [Member]	Sep. 30, 2014 Fair Value, Measurements, Recurring [Member] Parent Company [Member] Total [Member] Interest Rate Contract [Member]	Dec. 31, 2013 Fair Value, Measurements, Recurring [Member] Parent Company [Member] Total [Member] Interest Rate Contract [Member]	Sep. 30, 2014 Fair Value, Measurements, Recurring [Member] Subsidiaries [Member] Level 2 [Member]	Dec. 31, 2013 Fair Value, Measurements, Recurring [Member] Subsidiaries [Member] Level 2 [Member]	Sep. 30, 2014 Fair Value, Measurements, Recurring [Member] Subsidiaries [Member] Level 2 [Member] Commodity Contract [Member] Electric portfolio [Member]	Dec. 31, 2013 Fair Value, Measurements, Recurring [Member] Subsidiaries [Member] Level 2 [Member] Commodity Contract [Member] Electric portfolio [Member]	Sep. 30, 2014 Fair Value, Measurements, Recurring [Member] Subsidiaries [Member] Level 2 [Member] Commodity Contract [Member] Natural gas portfolio [Member]	Dec. 31, 2013 Fair Value, Measurements, Recurring [Member] Subsidiaries [Member] Level 2 [Member] Commodity Contract [Member] Natural gas portfolio [Member]	Sep. 30, 2014 Fair Value, Measurements, Recurring [Member] Subsidiaries [Member] Level 3 [Member]	Dec. 31, 2013 Fair Value, Measurements, Recurring [Member] Subsidiaries [Member] Level 3 [Member]	Sep. 30, 2014 Fair Value, Measurements, Recurring [Member] Subsidiaries [Member] Level 3 [Member] Commodity Contract [Member] Electric portfolio [Member]		Dec. 31, 2013 Fair Value, Measurements, Recurring [Member] Subsidiaries [Member] Level 3 [Member] Commodity Contract [Member] Electric portfolio [Member]		Sep. 30, 2014 Fair Value, Measurements, Recurring [Member] Subsidiaries [Member] Level 3 [Member] Commodity Contract [Member] Natural gas portfolio [Member]		Dec. 31, 2013 Fair Value, Measurements, Recurring [Member] Subsidiaries [Member] Level 3 [Member] Commodity Contract [Member] Natural gas portfolio [Member]		Sep. 30, 2014 Fair Value, Measurements, Recurring [Member] Subsidiaries [Member] Total [Member]	Dec. 31, 2013 Fair Value, Measurements, Recurring [Member] Subsidiaries [Member] Total [Member]	Sep. 30, 2014 Fair Value, Measurements, Recurring [Member] Subsidiaries [Member] Total [Member] Commodity Contract [Member] Electric portfolio [Member]	Dec. 31, 2013 Fair Value, Measurements, Recurring [Member] Subsidiaries [Member] Total [Member] Commodity Contract [Member] Electric portfolio [Member]	Sep. 30, 2014 Fair Value, Measurements, Recurring [Member] Subsidiaries [Member] Total [Member] Commodity Contract [Member] Natural gas portfolio [Member]	Dec. 31, 2013 Fair Value, Measurements, Recurring [Member] Subsidiaries [Member] Total [Member] Commodity Contract [Member] Natural gas portfolio [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Unrealized Gain (Loss) on Derivatives and Commodity Contracts									$ (3,300,000)		$ (800,000)		$ (3,300,000)		$ (15,000,000)
Derivative Assets																									19,550,000	26,600,000																	13,297,000	20,109,000	2,906,000	14,661,000	10,391,000	5,448,000	6,253,000	6,491,000	4,254,000	[1]	3,818,000	[1]	1,999,000	[1]	2,673,000	[1]	19,550,000	26,600,000	7,160,000	18,479,000	12,390,000	8,121,000
Derivative Liability																									52,307,000	72,988,000	9,560,000	[2]	13,223,000	[2]	9,560,000	13,223,000	9,560,000	13,223,000	0	0	0	0	9,560,000	13,223,000	9,560,000	13,223,000	31,109,000	50,715,000	15,711,000	18,073,000	15,398,000	32,642,000	21,198,000	22,273,000	17,461,000	[1]	19,239,000	[1]	3,737,000	[1]	3,034,000	[1]	52,307,000	72,988,000	33,172,000	37,312,000	19,135,000	35,676,000
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance at beginning of period	(4,966,000)		(39,772,000)		(15,782,000)		(35,526,000)		(4,693,000)		(36,899,000)		(15,421,000)		(33,924,000)		(273,000)		(2,873,000)		(361,000)		(1,602,000)
Included in earnings	(3,116,000)	[3]	(392,000)	[3]	1,939,000	[3]	(11,593,000)	[3]	(3,116,000)	[3]	(392,000)	[3]	1,939,000	[3]	(11,593,000)	[3]	0	[3]	0	[3]	0	[3]	0	[3]
Included in regulatory assets/liabilities	(725,000)		(957,000)		1,654,000		(967,000)		0		0		0		0		(725,000)		(957,000)		1,654,000		(967,000)
Settlements	(1,645,000)	[4]	(804,000)	[4]	(142,000)	[4]	7,030,000	[4]	(965,000)	[4]	(1,270,000)	[4]	1,114,000	[4]	7,792,000	[4]	(680,000)	[4]	466,000	[4]	(1,256,000)	[4]	(762,000)	[4]
Transferred into Level 3	2,055,000		730,000		4,570,000		(7,799,000)		2,055,000		730,000		5,155,000		(7,799,000)		0		0		(585,000)		0
Transferred out of Level 3	(6,548,000)		9,277,000		(7,184,000)		16,937,000		(6,488,000)		8,712,000		(5,994,000)		16,405,000		(60,000)		565,000		(1,190,000)		532,000
Balance at end of period	$ (14,945,000)		$ (31,918,000)		$ (14,945,000)		$ (31,918,000)		$ (13,207,000)		$ (29,119,000)		$ (13,207,000)		$ (29,119,000)		$ (1,738,000)		$ (2,799,000)		$ (1,738,000)		$ (2,799,000)

[1] 1 The valuation techniques, unobservable inputs and ranges are the same for asset and liability positions

[2] 2 Interest Rate Swap Contracts are only held at Puget Energy.

[3] 1 Income Statement location: Unrealized (gain) loss on derivative instruments, net. Includes unrealized gains (losses) on derivatives still held in position as of the reporting date for electric derivatives of $(3.3) million and $(0.8) million for the three months ended September 30, 2014 and 2013, respectively. 2 Income Statement location: Unrealized (gain) loss on derivative instruments, net. Includes unrealized gains (losses) on derivatives still held in position as of the reporting date for electric derivatives of $(3.3) million and $(15.0) million for the nine months ended September 30, 2014 and 2013, respectively.

[4] 3 The Company had no purchases, sales or issuances during the reported periods