Utility Plant (Details) (USD $)	12 Months Ended
	Dec. 31, 2014		Dec. 31, 2013
Public Utility, Property, Plant and Equipment
Accumulated amortization of capital leases	28,400,000		$ 20,800,000
Utility Plant
Distribution plant	4,748,988,000		4,448,451,000
Production plant	2,973,853,000		2,966,223,000
Transmission plant	1,189,296,000		1,043,605,000
General plant	481,116,000		504,965,000
Intangible plant (including capitalized software)	311,959,000		316,614,000
Plant acquisition adjustment	242,826,000		242,826,000
Underground storage	28,859,000		27,857,000
Liquefied natural gas storage	12,628,000		12,622,000
Plant held for future use	54,996,000		28,742,000
Recoverable cushion gas	8,655,000		8,655,000
Public Utilities, Property, Plant and Equipment, Other Property, Plant and Equipment	91,519,000		124,589,000
Public Utilities, Property, Plant and Equipment Grant	(105,659,000)		0
Capital leases, net of accumulated amortization	9,473,000	[1]	17,051,000	[1]
Less: Accumulated depreciation and amortization	(1,611,220,000)		(1,373,178,000)
Subtotal	8,437,289,000		8,369,022,000
Construction work in progress	239,690,000		310,318,000
Net utility plant	8,676,979,000		8,679,340,000
Minimum
Public Utility, Property, Plant and Equipment
Distribution plant, Estimated Useful Life	10 years
Production plant, Estimated Useful Life	25 years
Transmission plant, Estimated Useful Life	45 years
General plant, Estimated Useful Life	5 years
Intangible plant (including capitalized software), Estimated Useful Life	3 years
Plant acquisition adjustment, Estimated Useful Life	7 years
Underground storage, Estimated Useful Life	25 years
Liquefied natural gas storage, Estimated Useful Life	25 years
Public Utilities, Property, Plant and Equipment, Plant Not Classified, Estimated Useful Life	1 year
Capital leases, net of accumulated amortization, Estimated Useful Life	1 year	[1]
Maximum
Public Utility, Property, Plant and Equipment
Distribution plant, Estimated Useful Life	50 years
Production plant, Estimated Useful Life	125 years
Transmission plant, Estimated Useful Life	65 years
General plant, Estimated Useful Life	35 years
Intangible plant (including capitalized software), Estimated Useful Life	50 years
Plant acquisition adjustment, Estimated Useful Life	30 years
Underground storage, Estimated Useful Life	60 years
Liquefied natural gas storage, Estimated Useful Life	45 years
Public Utilities, Property, Plant and Equipment, Plant Not Classified, Estimated Useful Life	100 years
Capital leases, net of accumulated amortization, Estimated Useful Life	5 years	[1]
PUGET SOUND ENERGY, INC.
Public Utility, Property, Plant and Equipment
Accumulated amortization of capital leases	28,400,000		20,800,000
Utility Plant
Distribution plant	6,417,551,000		6,127,732,000
Production plant	3,907,224,000		3,948,270,000
Transmission plant	1,306,009,000		1,162,929,000
General plant	553,130,000		599,156,000
Intangible plant (including capitalized software)	304,135,000		309,972,000
Plant acquisition adjustment	282,792,000		282,792,000
Underground storage	42,494,000		41,501,000
Liquefied natural gas storage	14,498,000		14,492,000
Plant held for future use	55,148,000		28,895,000
Recoverable cushion gas	8,655,000		8,655,000
Public Utilities, Property, Plant and Equipment, Other Property, Plant and Equipment	91,519,000		124,589,000
Public Utilities, Property, Plant and Equipment Grant	(105,659,000)		0
Capital leases, net of accumulated amortization	9,473,000	[1]	17,051,000	[1]
Less: Accumulated depreciation and amortization	(4,449,680,000)		(4,297,012,000)
Subtotal	8,437,289,000		8,369,022,000
Construction work in progress	239,690,000		310,318,000
Net utility plant	8,676,979,000		$ 8,679,340,000

[1] Accumulated amortization of capital leases at Puget Energy was $28.4 million in 2014 and $20.8 million in 2013. Accumulated amortization of capital leases at PSE was $28.4 million in 2014 and $20.8 million in 2013.