Fair Value Measurements Valuation Technicques for Measurement with Unobservable Inputs (Details) (USD $)	6 Months Ended				6 Months Ended
	Jun. 30, 2012	Jun. 30, 2012 Carrying Value [Member]	Jun. 30, 2012 Fair Value [Member]	Mar. 31, 2012 Fair Value [Member]	Jun. 30, 2012 Discounted cash flow [Member] Low [Member]	Jun. 30, 2012 Discounted cash flow [Member] High [Member]	Jun. 30, 2012 Discounted cash flow [Member] Weighted Average [Member]	Jun. 30, 2012 Electric portfolio [Member] Discounted cash flow [Member] Low [Member]	Jun. 30, 2012 Electric portfolio [Member] Discounted cash flow [Member] High [Member]	Jun. 30, 2012 Electric portfolio [Member] Discounted cash flow [Member] Weighted Average [Member]	Jun. 30, 2012 Natural gas portfolio [Member] Discounted cash flow [Member] Low [Member]	Jun. 30, 2012 Natural gas portfolio [Member] Discounted cash flow [Member] High [Member]	Jun. 30, 2012 Natural gas portfolio [Member] Discounted cash flow [Member] Weighted Average [Member]	Jun. 30, 2012 Level 3 [Member] Fair Value, Measurements, Recurring [Member] PUGET ENERGY [Member]	Dec. 31, 2011 Level 3 [Member] Fair Value, Measurements, Recurring [Member] PUGET ENERGY [Member]	Jun. 30, 2012 Natural gas portfolio [Member] Level 3 [Member] Fair Value, Measurements, Recurring [Member] PUGET ENERGY [Member] Commodity Contract [Member]		Dec. 31, 2011 Natural gas portfolio [Member] Level 3 [Member] Fair Value, Measurements, Recurring [Member] PUGET ENERGY [Member] Commodity Contract [Member]	Jun. 30, 2012 Electric portfolio [Member] Level 3 [Member] Fair Value, Measurements, Recurring [Member] PUGET ENERGY [Member] Commodity Contract [Member]		Dec. 31, 2011 Electric portfolio [Member] Level 3 [Member] Fair Value, Measurements, Recurring [Member] PUGET ENERGY [Member] Commodity Contract [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Derivative Assets														$ 15,463,000	$ 14,391,000	$ 6,025,000	[1]	$ 6,011,000	$ 9,438,000	[1]	$ 8,380,000
Derivative Liabilities														98,735,000	109,743,000	8,844,000	[1]	11,052,000	89,891,000	[1]	98,691,000
Price (per MWh)					10.36	49.78	34.98	6.11	46.86	29.93
Price (per MMBtu)											1.77	4.79	3.88
Fair Value Measurements, Sensitivity Analysis, Hypothetical Increase or Decrease of Market Prices, Result on Fair Value	18,700,000
Finite-lived Intangible Assets, Fair Value Disclosure		113,300,000	96,700,000
Impairment of Intangible Assets, Finite-lived	16,600,000
Fair Value Inputs, Power Contract Costs					3,185,000	5,030,000	4,663,000
Long-term Purchase Contracts, Fair Value Disclosure				$ 513,600,000

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