Fair Value Measurements Assets and Liabilities (Details) - USD ($) $ in Thousands		3 Months Ended				6 Months Ended
		Jun. 30, 2015		Jun. 30, 2014		Jun. 30, 2015		Jun. 30, 2014		Dec. 31, 2014
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance at beginning of period		$ (17,692)		$ (15,709)		$ (14,100)		$ (15,782)
Included in earnings		(4,064)	[1]	7,800	[1]	(9,102)	[2]	5,055	[2]
Included in regulatory assets/liabilities		2,813		2,120		2,938		2,379
Settlements	[3]	(337)		1,591		(133)		1,502
Transferred into Level 3		0		0		(787)		2,515
Transferred out of Level 3		4,733		(768)		6,637		(635)
Balance at end of period		(14,547)		(4,966)		(14,547)		(4,966)
Electric portfolio [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Unrealized Gain (Loss) on Derivatives and Commodity Contracts		(3,800)		4,700		(8,800)		100
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance at beginning of period		(16,091)		(14,606)		(12,061)		(15,421)
Included in earnings		(4,064)	[1]	7,800	[1]	(9,102)	[2]	5,055	[2]
Included in regulatory assets/liabilities		0		0		0		0
Settlements	[3]	52		1,757		165		2,078
Transferred into Level 3		0		0		(787)		3,100
Transferred out of Level 3		4,733		356		6,415		495
Balance at end of period		(15,370)		(4,693)		(15,370)		(4,693)
Natural gas portfolio [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance at beginning of period		(1,601)		(1,103)		(2,039)		(361)
Included in earnings		0	[1]	0	[1]	0	[2]	0	[2]
Included in regulatory assets/liabilities		2,813		2,120		2,938		2,379
Settlements	[3]	(389)		(166)		(298)		(576)
Transferred into Level 3		0		0		0		(585)
Transferred out of Level 3		0		(1,124)		222		(1,130)
Balance at end of period		823		$ (273)		823		$ (273)
Commodity Contract [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Assets		21,088				21,088				$ 24,348
Derivative Liability		167,748				167,748				196,035
Interest Rate Contract [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Liability	[4]	8,294				8,294				9,073
Fair Value, Measurements, Recurring [Member] | Parent Company [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Liability		8,294				8,294				9,073
Fair Value, Measurements, Recurring [Member] | Parent Company [Member] | Level 2 [Member] | Interest Rate Contract [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Liability		8,294				8,294				9,073
Fair Value, Measurements, Recurring [Member] | Parent Company [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Liability		0				0				0
Fair Value, Measurements, Recurring [Member] | Parent Company [Member] | Level 3 [Member] | Interest Rate Contract [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Liability		0				0				0
Fair Value, Measurements, Recurring [Member] | Parent Company [Member] | Total [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Liability		8,294				8,294				9,073
Fair Value, Measurements, Recurring [Member] | Parent Company [Member] | Total [Member] | Interest Rate Contract [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Liability		8,294				8,294				9,073
Fair Value, Measurements, Recurring [Member] | Subsidiaries [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Assets		14,117				14,117				19,718
Derivative Liability		146,230				146,230				177,303
Fair Value, Measurements, Recurring [Member] | Subsidiaries [Member] | Level 2 [Member] | Commodity Contract [Member] | Electric portfolio [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Assets		8,777				8,777				1,654
Derivative Liability		83,374				83,374				91,998
Fair Value, Measurements, Recurring [Member] | Subsidiaries [Member] | Level 2 [Member] | Commodity Contract [Member] | Natural gas portfolio [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Assets		5,340				5,340				18,064
Derivative Liability		62,856				62,856				85,305
Fair Value, Measurements, Recurring [Member] | Subsidiaries [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Assets		6,971				6,971				4,630
Derivative Liability		21,518				21,518				18,732
Fair Value, Measurements, Recurring [Member] | Subsidiaries [Member] | Level 3 [Member] | Commodity Contract [Member] | Electric portfolio [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Assets		2,672	[5]			2,672	[5]			3,168	[6]
Derivative Liability		18,042	[5]			18,042	[5]			15,230	[6]
Fair Value, Measurements, Recurring [Member] | Subsidiaries [Member] | Level 3 [Member] | Commodity Contract [Member] | Natural gas portfolio [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Assets		4,299	[5]			4,299	[5]			1,462	[6]
Derivative Liability		3,476	[5]			3,476	[5]			3,502	[6]
Fair Value, Measurements, Recurring [Member] | Subsidiaries [Member] | Total [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Assets		21,088				21,088				24,348
Derivative Liability		167,748				167,748				196,035
Fair Value, Measurements, Recurring [Member] | Subsidiaries [Member] | Total [Member] | Commodity Contract [Member] | Electric portfolio [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Assets		11,449				11,449				4,822
Derivative Liability		101,416				101,416				107,228
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]
Derivative Assets		9,639				9,639				19,526
Derivative Liability		$ 66,332				$ 66,332				$ 88,807

[1] 1 Income Statement locations: 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 $(3.8) million and $4.7 million for the three months ended June 30, 2015 and 2014, respectively.

[2] 2 Income Statement locations: 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 $(8.8) million and $0.1 million for the six months ended June 30, 2015 and 2014, respectively.

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

[4] 2 Interest rate swap contracts are only held at Puget Energy.

[5] 1 The valuation techniques, unobservable inputs and ranges are the same for asset and liability positions

[6] 1 The valuation techniques, unobservable inputs and ranges are the same for asset and liability positions.