Accounting for Derivative Instruments and Hedging Activities Derivative Assets and Liabilities (Details) (USD $)	Jun. 30, 2012		Dec. 31, 2011
Derivative [Line Items]
Assets, Current	$ 6,973,000		$ 6,647,000
Assets, Long-term	15,981,000		10,084,000
Liabilities, Current	277,246,000		327,089,000
Liabilities, Long-term	113,209,000		196,558,000
PUGET SOUND ENERGY, INC. [Member]
Derivative [Line Items]
Assets, Current	6,973,000		6,647,000
Assets, Long-term	15,981,000		10,084,000
Liabilities, Current	271,023,000		301,879,000
Liabilities, Long-term	99,285,000		169,359,000
Offsetting regulatory assets	150,800,000		200,900,000
Not Designated as Hedging Instrument [Member]
Derivative [Line Items]
Assets	22,954,000	[1],[2]	16,731,000	[1],[2]
Liabilities	370,308,000	[2],[3]	471,238,000	[2],[3]
Not Designated as Hedging Instrument [Member] | Interest rate swaps [Member] | PUGET ENERGY [Member]
Derivative [Line Items]
Assets, Current	0	[1]	0	[1]
Assets, Long-term	0	[1]	0	[1]
Assets	0		0	[1]
Liabilities, Current	6,223,000	[3]	25,210,000	[3]
Liabilities, Long-term	13,924,000	[3]	27,199,000	[3]
Liabilities	20,147,000		52,409,000	[3]
Not Designated as Hedging Instrument [Member] | Electric portfolio [Member]
Derivative [Line Items]
Assets, Current	4,031,000	[1]	5,212,000	[1]
Assets, Long-term	9,523,000	[1]	5,508,000	[1]
Liabilities, Current	160,033,000	[3]	173,582,000	[3]
Liabilities, Long-term	50,048,000	[3]	90,752,000	[3]
Not Designated as Hedging Instrument [Member] | Natural gas portfolio [Member]
Derivative [Line Items]
Assets, Current	2,942,000	[1],[2]	1,435,000	[1],[2]
Assets, Long-term	6,458,000	[1],[2]	4,576,000	[1],[2]
Liabilities, Current	110,990,000	[2],[3]	128,297,000	[2],[3]
Liabilities, Long-term	$ 49,237,000	[2],[3]	$ 78,607,000	[2],[3]

[1] Balance sheet location: Unrealized gain on derivative instruments.

[2] PSE had a net derivative liability and an offsetting regulatory asset of $150.8 million at June 30, 2012 and $200.9 million at December 31, 2011 related to financial contracts used to economically hedge the cost of physical gas purchased to serve natural gas customers. All fair value adjustments on derivatives relating to the natural gas business have been reclassified to a deferred account in accordance with ASC 980, “Regulated Operations” (ASC 980) due to the Purchased Gas Adjustment (PGA) mechanism. All increases and decreases in the cost of natural gas supply are passed on to customers with the PGA mechanism and the gains and losses on the hedges in future periods will be recorded as gas costs.

[3] Balance sheet location: Unrealized loss on derivative instruments.