Utility Plant (Details) (USD $)					12 Months Ended
	Dec. 31, 2012		Dec. 31, 2011		Dec. 31, 2012 Minimum		Dec. 31, 2012 Maximum		Dec. 31, 2012 PUGET SOUND ENERGY, INC.		Dec. 31, 2011 PUGET SOUND ENERGY, INC.
Public Utility, Property, Plant and Equipment
Distribution plant, Estimated Useful Life					10 years		50 years
Production plant, Estimated Useful Life					25 years		125 years
Transmission plant, Estimated Useful Life					45 years		65 years
General plant, Estimated Useful Life					5 years		35 years
Intangible plant (including capitalized software), Estimated Useful Life					3 years		50 years
Plant acquisition adjustment, Estimated Useful Life					7 years		30 years
Underground storage, Estimated Useful Life					25 years		60 years
Liquefied natural gas storage, Estimated Useful Life					25 years		45 years
Capital leases, net of accumulated amortization, Estimated Useful Life					1 year	[1]	5 years	[1]
Utility Plant
Distribution plant	$ 4,276,123,000		$ 4,552,087,000						$ 5,993,055,000		$ 6,279,340,000
Production plant	2,480,135,000		1,618,196,000						3,464,528,000		2,616,855,000
Transmission plant	984,018,000		391,080,000						1,108,104,000		516,461,000
General plant	445,982,000		402,309,000						543,195,000		499,559,000
Intangible plant (including capitalized software)	181,884,000		152,025,000						181,596,000		187,948,000
Plant acquisition adjustment	242,659,000		211,807,000						282,624,000		251,772,000
Underground storage	27,331,000		27,139,000						40,987,000		40,815,000
Liquefied natural gas storage	12,622,000		12,622,000						14,492,000		14,492,000
Plant held for future use	18,416,000		18,381,000						18,568,000		18,534,000
Recoverable cushion gas	8,655,000		8,514,000						8,655,000		8,514,000
Plant not classified	155,626,000		38,998,000						155,625,000		38,999,000
Capital leases, net of accumulated amortization	24,629,000	[1]	32,208,000	[1]					24,629,000	[1]	32,207,000	[1]
Less: Accumulated depreciation and amortization	(1,067,424,000)		(674,783,000)						(4,045,402,000)		(3,714,913,000)
Subtotal	7,790,656,000		6,790,583,000						7,790,656,000		6,790,583,000
Construction work in progress	766,035,000		1,282,462,000						766,035,000		1,282,462,000
Net utility plant	8,556,691,000		8,073,045,000						8,556,691,000		8,073,045,000
Accumulated amortization of capital leases	7,600,000		5,700,000						7,600,000		5,700,000
Amount of acquisition adjustments	90,000,000
Carrying value of property, plant and equipment, held for sale	$ 47,400,000

[1] Accumulated amortization of capital leases at Puget Energy was $7.6 million in 2012 and $5.7 million in 2011. Accumulated amortization of capital leases at PSE was $7.6 million in 2012 and $5.7 million in 2011.