Accounting for Derivative Instruments and Hedging Activities Recognized in Statement of Income (Details) (USD $)	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Derivative Instruments, (Loss) Gain [Line Items]
Document Period End Date			Jun. 30, 2013
Unrealized (gain) loss on derivative instruments	$ 27,376,000	$ (64,076,000)	$ (48,316,000)	$ (59,350,000)
PUGET ENERGY [Member]
Derivative Instruments, (Loss) Gain [Line Items]
Derivative Instruments, Amount Not Designated as Normal Purchase, Normal Sale			2,200,000
Subsidiaries [Member]
Derivative Instruments, (Loss) Gain [Line Items]
Document Period End Date			Jun. 30, 2013
Unrealized (gain) loss on derivative instruments	27,376,000	(59,850,000)	(45,365,000)	(49,715,000)
Not Designated as Hedging Instrument [Member] | PUGET ENERGY [Member]
Derivative Instruments, (Loss) Gain [Line Items]
Unrealized (gain) loss on derivative instruments	28,876,000	(4,356,000)	(1,143,000)	79,762,000
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	(1,232,000)	7,297,000	(2,260,000)	6,770,000
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	(1,902,000)	9,902,000	676,000	19,264,000
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	27,376,000	(64,076,000)	(48,316,000)	(57,199,000)
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	930,000	2,981,000	13,568,000	25,974,000
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	3,704,000	39,540,000	35,189,000	84,953,000
Not Designated as Hedging Instrument [Member] | Subsidiaries [Member]
Derivative Instruments, (Loss) Gain [Line Items]
Unrealized (gain) loss on derivative instruments	32,010,000	(17,329,000)	3,392,000	61,212,000
Not Designated as Hedging Instrument [Member] | Subsidiaries [Member] | Commodity Contract [Member] | Unrealized (Gain) Loss on Derivative Instruments, Net [Member]
Derivative Instruments, (Loss) Gain [Line Items]
Unrealized (gain) loss on derivative instruments	27,376,000	(59,850,000)	(45,365,000)	(49,715,000)
Not Designated as Hedging Instrument [Member] | Subsidiaries [Member] | Commodity Contract [Member] | Electric generation fuel [Member]
Derivative Instruments, (Loss) Gain [Line Items]
Unrealized (gain) loss on derivative instruments	930,000	2,981,000	13,568,000	25,974,000
Not Designated as Hedging Instrument [Member] | Subsidiaries [Member] | Commodity Contract [Member] | Purchased electricity [Member]
Derivative Instruments, (Loss) Gain [Line Items]
Unrealized (gain) loss on derivative instruments	3,704,000	39,540,000	35,189,000	84,953,000
Cash Flow Hedging [Member] | PUGET ENERGY [Member]
Derivative Instruments, (Loss) Gain [Line Items]
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net	(1,325,000)	(11,093,000)	(2,475,000)	(14,651,000)
Cash Flow Hedging [Member] | PUGET ENERGY [Member] | Interest expense [Member]
Derivative Instruments, (Loss) Gain [Line Items]
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net		(10,905,000)		(14,763,000)
Cash Flow Hedging [Member] | PUGET ENERGY [Member] | Electric generation fuel [Member]
Derivative Instruments, (Loss) Gain [Line Items]
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net	0	0	0	100,000
Cash Flow Hedging [Member] | PUGET ENERGY [Member] | Purchased electricity [Member]
Derivative Instruments, (Loss) Gain [Line Items]
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net		(188,000)		12,000
Cash Flow Hedging [Member] | Subsidiaries [Member]
Derivative Instruments, (Loss) Gain [Line Items]
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net	(122,000)	(4,536,000)	(3,030,000)	(7,615,000)
Cash Flow Hedging [Member] | Subsidiaries [Member] | Interest expense [Member]
Derivative Instruments, (Loss) Gain [Line Items]
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net		(122,000)		(244,000)
Cash Flow Hedging [Member] | Subsidiaries [Member] | Electric generation fuel [Member]
Derivative Instruments, (Loss) Gain [Line Items]
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net	0	(4,414,000)	0	97,000
Cash Flow Hedging [Member] | Subsidiaries [Member] | Purchased electricity [Member]
Derivative Instruments, (Loss) Gain [Line Items]
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net	$ 0	$ 0		$ (7,468,000)