Accounting for Derivative Instruments and Hedging Activities Recognized in Other Comprehensive Income (Details) (USD $)	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Derivative Instruments, Gain (Loss) [Line Items]
Document Period End Date			Sep. 30, 2013
Interest rate contracts: [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Other Comprehensive Income Reclassification Of Net Unrealized Gain Loss On Interest Rate Swaps During Period Net Of Tax	$ (811,000)	$ (1,055,000)	$ (2,526,000)	$ (10,651,000)
PUGET ENERGY [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Cash Flow Hedge Loss to be Reclassified within Twelve Months			(1,500,000)
Subsidiaries [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Document Period End Date			Sep. 30, 2013
Cash Flow Hedge Loss to be Reclassified within Twelve Months			(2,200,000)
Cash Flow Hedging [Member] | PUGET ENERGY [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net	(1,247,000)	(2,015,000)	(3,722,000)	(16,666,000)
Cash Flow Hedging [Member] | PUGET ENERGY [Member] | Interest expense [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net		(1,623,000)		(16,386,000)
Cash Flow Hedging [Member] | PUGET ENERGY [Member] | Electric generation fuel [Member]
Derivative Instruments, Gain (Loss) [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, Gain (Loss) [Line Items]
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net		(392,000)		(380,000)
Cash Flow Hedging [Member] | Subsidiaries [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net	(122,000)	(2,362,000)	(3,152,000)	(9,977,000)
Cash Flow Hedging [Member] | Subsidiaries [Member] | Interest expense [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net		(122,000)		(366,000)
Cash Flow Hedging [Member] | Subsidiaries [Member] | Electric generation fuel [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net	0	0	0	97,000
Cash Flow Hedging [Member] | Subsidiaries [Member] | Purchased electricity [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net		(2,240,000)		(9,708,000)
Revolving Credit Facility [Member] | Parent [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Line of Credit Facility, Decrease, Repayments	80,000,000
Line of Credit Facility, Amount Outstanding	299,000,000		299,000,000
Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member] | Revolving Credit Facility [Member] | PUGET ENERGY [Member] | Interest rate contracts: [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Other Comprehensive Income Reclassification Of Net Unrealized Gain Loss On Interest Rate Swaps During Period Net Of Tax	$ (500,000)