Accounting for Derivative Instruments and Hedging Activities Recognized in Statement of Income (Details) (USD $)	3 Months Ended
	Mar. 31, 2013		Mar. 31, 2012
Derivative Instruments, (Loss) Gain [Line Items]
Unrealized (gain) loss on derivative instruments	$ (75,692,000)		$ 4,726,000
PUGET ENERGY [Member]
Derivative Instruments, (Loss) Gain [Line Items]
Derivative Instruments, Amount Not Designated as Normal Purchase, Normal Sale			2,200,000
PUGET SOUND ENERGY, INC. [Member]
Derivative Instruments, (Loss) Gain [Line Items]
Unrealized (gain) loss on derivative instruments	(72,740,000)		10,135,000
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	(1,028,000)		(527,000)
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	2,578,000		6,641,000
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	(75,692,000)	[1]	6,876,000	[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	12,638,000		22,993,000
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	31,485,000		45,413,000
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	(72,740,000)		10,135,000
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	12,638,000		22,993,000
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	31,485,000		45,413,000
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	(1,150,000)		(3,559,000)
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	(1,314,000)		(3,859,000)
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		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	164,000		200,000
Cash Flow Hedging [Member] | PUGET SOUND ENERGY, INC. [Member]
Derivative Instruments, (Loss) Gain [Line Items]
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net	(2,908,000)		(3,080,000)
Cash Flow Hedging [Member] | PUGET SOUND ENERGY, INC. [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)		(122,000)
Cash Flow Hedging [Member] | PUGET SOUND ENERGY, INC. [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		97,000
Cash Flow Hedging [Member] | PUGET SOUND ENERGY, INC. [Member] | Purchased electricity [Member]
Derivative Instruments, (Loss) Gain [Line Items]
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net	$ (2,786,000)		$ (3,055,000)

[1]