Fair Value Measurements Unobservable Input Reconciliation (Details) (USD $)	3 Months Ended				6 Months Ended				3 Months Ended				6 Months Ended				3 Months Ended				6 Months Ended						6 Months Ended
	Jun. 30, 2013		Jun. 30, 2012		Jun. 30, 2013		Jun. 30, 2012		Jun. 30, 2013 Electric portfolio [Member]		Jun. 30, 2012 Electric portfolio [Member]		Jun. 30, 2013 Electric portfolio [Member]		Jun. 30, 2012 Electric portfolio [Member]		Jun. 30, 2013 Natural gas portfolio [Member]		Jun. 30, 2012 Natural gas portfolio [Member]		Jun. 30, 2013 Natural gas portfolio [Member]		Jun. 30, 2012 Natural gas portfolio [Member]		Jun. 30, 2013 Commodity Contract [Member]	Dec. 31, 2012 Commodity Contract [Member]	Jun. 30, 2013 High [Member] Discounted cash flow [Member]	Jun. 30, 2013 High [Member] Discounted cash flow [Member] Natural gas portfolio [Member]	Jun. 30, 2013 High [Member] Discounted cash flow [Member] Electric portfolio [Member]	Jun. 30, 2013 Weighted Average [Member] Discounted cash flow [Member]	Jun. 30, 2013 Weighted Average [Member] Discounted cash flow [Member] Natural gas portfolio [Member]	Jun. 30, 2013 Weighted Average [Member] Discounted cash flow [Member] Electric portfolio [Member]	Jun. 30, 2013 Low [Member] Discounted cash flow [Member]	Jun. 30, 2013 Low [Member] Discounted cash flow [Member] Natural gas portfolio [Member]	Jun. 30, 2013 Low [Member] Discounted cash flow [Member] Electric portfolio [Member]	Jun. 30, 2013 Fair Value, Measurements, Recurring [Member] PUGET ENERGY [Member] Level 3 [Member]	Dec. 31, 2012 Fair Value, Measurements, Recurring [Member] PUGET ENERGY [Member] Level 3 [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Derivative Assets																									$ 16,891,000	$ 21,683,000
Derivative Liabilities																																				0	0
Price (per MMBtu)																												4.71			3.99			2.97
Price (per MWh)																											65.35		44.76	48.47		32.46	30.85		13.09
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance at beginning of period	(27,976,000)		(110,531,000)		(35,526,000)		(95,352,000)		(26,442,000)		(107,364,000)		(33,924,000)		(90,311,000)		(1,534,000)		(3,167,000)		(1,602,000)		(5,041,000)
Included in earnings	(12,799,000)	[1]	5,077,000	[1]	(11,201,000)	[1]	(16,870,000)	[1]	(12,799,000)	[1]	5,077,000	[1]	(11,201,000)	[1]	(16,870,000)	[1]	0	[1]	0	[1]	0	[1]	0	[1]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Gain (Loss) Included in Regulatory Assets (Liabilities)	(684,000)		(4,000)		(10,000)		(1,287,000)		0		0		0		0		(684,000)		(4,000)		(10,000)		(1,287,000)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Settlements	2,183,000	[2]	14,696,000	[2]	7,834,000	[2]	35,520,000	[2]	2,678,000	[2]	14,372,000	[2]	9,062,000	[2]	35,415,000	[2]	(495,000)	[2]	324,000	[2]	(1,228,000)	[2]	105,000	[2]
Transferred into Level 3	(830,000)		(38,971,000)		(8,530,000)		(55,845,000)		(830,000)		(38,674,000)		(8,530,000)		(55,548,000)		0		(297,000)		0		(297,000)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Liability, Transfers out of Level 3	334,000		46,461,000		7,661,000		50,562,000		494,000		46,136,000		7,694,000		46,861,000		(160,000)		325,000		(33,000)		3,701,000
Balance at end of period	(39,772,000)		(83,272,000)		(39,772,000)		(83,272,000)		(36,899,000)		(80,453,000)		(36,899,000)		(80,453,000)		(2,873,000)		(2,819,000)		(2,873,000)		(2,819,000)
Unrealized (gain) loss on derivatives instuments, net									15,600,000		(6,200,000)		14,200,000		12,800,000
Fair Value Inputs, Power Contract Costs																											$ 6,845,000			$ 4,110,000			$ 389,000

[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 $(15.6) million and $6.2 million for the three months ended June 30, 2013 and 2012, 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 $(14.2) million and $(12.8) million for the six months ended June 30, 2013 and 2012, respectively.3

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