Summary of Significant Accounting Policies (Details) (USD $)	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011	Dec. 31, 2011
Schedule of Capitalization, Equity [Line Items]
Revenues	$ 678,617,000	$ 732,675,000	$ 1,727,129,000	$ 1,752,268,000
Operating Income (Loss)	159,876,000	114,693,000	368,897,000	332,837,000
Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]
Total, net of tax	(21,593,000)		(21,593,000)		(30,907,000)
PUGET ENERGY [Member]
Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]
Net unrealized loss on energy derivative instruments	(1,186,000)		(1,186,000)		(1,113,000)
Net unrealized loss on interest rate swaps	(5,003,000)		(5,003,000)		(14,599,000)
Net unrealized loss and prior service cost on pension plans	(15,404,000)		(15,404,000)		(15,195,000)
Total, net of tax	(21,593,000)		(21,593,000)		(30,907,000)
PUGET SOUND ENERGY, INC. [Member]
Schedule of Capitalization, Equity [Line Items]
Area of Service Territory (in sqmi)	6,000		6,000
Revenues	678,617,000	733,364,000	1,727,129,000	1,752,957,000
Operating Income (Loss)	153,306,000	107,380,000	354,549,000	297,817,000
Excise taxes collected	53,700,000	57,100,000	134,700,000	137,400,000
Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]
Net unrealized loss on energy derivative instruments	(8,143,000)		(8,143,000)		(12,934,000)
Net unrealized loss on interest rate swaps	(6,782,000)		(6,782,000)		(6,941,000)
Net unrealized loss and prior service cost on pension plans	(165,061,000)		(165,061,000)		(168,704,000)
Total, net of tax	(179,986,000)		(179,986,000)		(188,579,000)
PUGET SOUND ENERGY, INC. [Member] | Change in Accounting Estimate, Unbilled Revenues [Member]
Schedule of Capitalization, Equity [Line Items]
Revenues			4,400,000
Operating Income (Loss)			$ 2,900,000