Accounting for Derivative Instruments and Hedging Activities Recognized in Statement of Income (Details) (USD $)	3 Months Ended				6 Months Ended
	Jun. 30, 2012		Jun. 30, 2011		Jun. 30, 2012		Jun. 30, 2011
Derivative Instruments, (Loss) Gain [Line Items]
Unrealized (gain) loss on derivative instruments	$ (64,076,000)		$ (16,995,000)		$ (59,350,000)		$ (50,113,000)
PUGET ENERGY [Member]
Derivative Instruments, (Loss) Gain [Line Items]
Derivative Instruments, Amount Not Designated as Normal Purchase, Normal Sale	0		2,700,000		2,200,000		10,800,000
PUGET SOUND ENERGY, INC. [Member]
Derivative Instruments, (Loss) Gain [Line Items]
Unrealized (gain) loss on derivative instruments	(59,850,000)		(9,648,000)		(49,715,000)		(15,632,000)
Not Designated as Hedging Instrument [Member] | PUGET ENERGY [Member]
Derivative Instruments, (Loss) Gain [Line Items]
Unrealized (gain) loss on derivative instruments	(4,356,000)		61,802,000		79,762,000		96,844,000
Not Designated as Hedging Instrument [Member] | PUGET ENERGY [Member] | Other Income (Deductions) [Member] | Interest expense [Member]
Derivative Instruments, (Loss) Gain [Line Items]
Unrealized (gain) loss on derivative instruments	7,297,000		25,412,000		6,770,000		25,460,000
Not Designated as Hedging Instrument [Member] | PUGET ENERGY [Member] | Interest Rate Contract [Member] | Interest expense [Member]
Derivative Instruments, (Loss) Gain [Line Items]
Unrealized (gain) loss on derivative instruments	9,902,000		22,699,000		19,264,000		27,276,000
Not Designated as Hedging Instrument [Member] | PUGET ENERGY [Member] | Commodity Contract [Member] | Unrealized (Gain) Loss on Derivative Instruments, Net [Member]
Derivative Instruments, (Loss) Gain [Line Items]
Unrealized (gain) loss on derivative instruments	(64,076,000)	[1]	(14,275,000)	[1]	(57,199,000)	[1]	(39,344,000)	[1]
Not Designated as Hedging Instrument [Member] | PUGET ENERGY [Member] | Commodity Contract [Member] | Electric generation fuel [Member]
Derivative Instruments, (Loss) Gain [Line Items]
Unrealized (gain) loss on derivative instruments	2,981,000		8,808,000		25,974,000		49,622,000
Not Designated as Hedging Instrument [Member] | PUGET ENERGY [Member] | Commodity Contract [Member] | Purchased electricity [Member]
Derivative Instruments, (Loss) Gain [Line Items]
Unrealized (gain) loss on derivative instruments	39,540,000		19,158,000		84,953,000		33,830,000
Not Designated as Hedging Instrument [Member] | PUGET SOUND ENERGY, INC. [Member]
Derivative Instruments, (Loss) Gain [Line Items]
Unrealized (gain) loss on derivative instruments	(17,329,000)		18,318,000		61,212,000		67,820,000
Not Designated as Hedging Instrument [Member] | PUGET SOUND ENERGY, INC. [Member] | Commodity Contract [Member] | Unrealized (Gain) Loss on Derivative Instruments, Net [Member]
Derivative Instruments, (Loss) Gain [Line Items]
Unrealized (gain) loss on derivative instruments	(59,850,000)		(9,648,000)		(49,715,000)		(15,632,000)
Not Designated as Hedging Instrument [Member] | PUGET SOUND ENERGY, INC. [Member] | Commodity Contract [Member] | Electric generation fuel [Member]
Derivative Instruments, (Loss) Gain [Line Items]
Unrealized (gain) loss on derivative instruments	2,981,000		8,808,000		25,974,000		49,622,000
Not Designated as Hedging Instrument [Member] | PUGET SOUND ENERGY, INC. [Member] | Commodity Contract [Member] | Purchased electricity [Member]
Derivative Instruments, (Loss) Gain [Line Items]
Unrealized (gain) loss on derivative instruments	39,540,000		19,158,000		84,953,000		33,830,000
Designated as Hedging Instrument [Member] | PUGET ENERGY [Member] | Operating expense [Member]
Derivative Instruments, (Loss) Gain [Line Items]
Unrealized (gain) loss on derivative instruments	(64,076,000)		(16,995,000)		(59,350,000)		(50,113,000)
Designated as Hedging Instrument [Member] | PUGET ENERGY [Member] | Natural gas / Power NPNS [Member] | Operating expense [Member]
Derivative Instruments, (Loss) Gain [Line Items]
Unrealized (gain) loss on derivative instruments	0	[2]	(2,720,000)	[2]	(2,151,000)	[2]	(10,769,000)	[2]
Designated as Hedging Instrument [Member] | PUGET ENERGY [Member] | Natural gas for power generation [Member] | Operating expense [Member]
Derivative Instruments, (Loss) Gain [Line Items]
Unrealized (gain) loss on derivative instruments	(13,647,000)		1,261,000		(13,698,000)		(40,262,000)
Designated as Hedging Instrument [Member] | PUGET ENERGY [Member] | Power [Member] | Operating expense [Member]
Derivative Instruments, (Loss) Gain [Line Items]
Unrealized (gain) loss on derivative instruments	(50,429,000)		(15,536,000)		(43,501,000)		918,000
Designated as Hedging Instrument [Member] | PUGET ENERGY [Member] | Interest rate swaps [Member] | Interest expense [Member]
Derivative Instruments, (Loss) Gain [Line Items]
Unrealized (gain) loss on derivative instruments	(8,563,000)		14,171,000		(4,102,000)		12,245,000
Designated as Hedging Instrument [Member] | PUGET ENERGY [Member] | Interest rate swaps [Member] | Other Income (Deductions) [Member]
Derivative Instruments, (Loss) Gain [Line Items]
Unrealized (gain) loss on derivative instruments	925,000		16,126,000		(13,398,000)		14,326,000
Designated as Hedging Instrument [Member] | PUGET SOUND ENERGY, INC. [Member] | Operating expense [Member]
Derivative Instruments, (Loss) Gain [Line Items]
Unrealized (gain) loss on derivative instruments	(59,850,000)		(9,648,000)		(49,715,000)		(15,632,000)
Designated as Hedging Instrument [Member] | PUGET SOUND ENERGY, INC. [Member] | Natural gas for power generation [Member] | Operating expense [Member]
Derivative Instruments, (Loss) Gain [Line Items]
Unrealized (gain) loss on derivative instruments	(13,647,000)		1,476,000		(13,696,000)		(23,201,000)
Designated as Hedging Instrument [Member] | PUGET SOUND ENERGY, INC. [Member] | Power [Member] | Operating expense [Member]
Derivative Instruments, (Loss) Gain [Line Items]
Unrealized (gain) loss on derivative instruments	$ (46,203,000)		$ (11,124,000)		$ (36,019,000)		$ 7,569,000

[1] Differs from the amounts stated in the statements of income as it does not include amortization related to contracts that were recorded at fair value at the time of the February 2009 merger and subsequently designated as NPNS of $0.0 million and $2.2 million for the three and six months ended June 30, 2012 and $2.7 million and $10.8 million for the three and six months ended June 30, 2011, respectively.

[2] Amount represents amortization related to contracts that were recorded at fair value as of the date of the merger.