CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (Parenthetical) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Parent [Line Items]
Reclassification of net unrealized loss on interest rate swaps during the period, net of tax	$ 436	$ 568	$ 1,360	$ 5,735
Other comprehensive income (loss):
Income tax (benefit) expense	5,936	20,943	75,569	73,289
Net unrealized gain (loss) from pension and postretirement plans, tax	212	(672)	(197)	(784)
Other Comprehensive Income (Loss), Reclassification Adjustment on Derivatives Included in Net Income, Net of Tax	0	255	(107)	182
Reclassification of net unrealized loss on energy derivative instruments during the period, net of tax	0	(137)	57	98
PUGET ENERGY [Member]
Parent [Line Items]
Net current-period other comprehensive income (loss)	1,204		2,052
Subsidiaries [Member]
Parent [Line Items]
Net current-period other comprehensive income (loss)	3,485		10,719
Other comprehensive income (loss):
Income tax (benefit) expense	14,530	30,949	105,470	108,250
Net unrealized gain (loss) from pension and postretirement plans, tax	1,834	1,313	4,669	3,275
Other Comprehensive Income (Loss), Reclassification Adjustment on Derivatives Included in Net Income, Net of Tax	0	1,456	1,811	6,247
Amortization Of Financing Cash Flow Hedge Contracts To Earnings Tax	43	43	128	128
Reclassification of net unrealized loss on energy derivative instruments during the period, net of tax	0	784	976	3,364
Reclassification out of Accumulated Other Comprehensive Income [Member] | Accumulated Defined Benefit Plans Adjustment [Member] | PUGET ENERGY [Member]
Other comprehensive income (loss):
Income tax (benefit) expense	(212)		(636)
Reclassification out of Accumulated Other Comprehensive Income [Member] | Accumulated Defined Benefit Plans Adjustment [Member] | Subsidiaries [Member]
Other comprehensive income (loss):
Income tax (benefit) expense	(1,834)		(5,501)
Energy Related Derivative [Member] | Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member] | PUGET ENERGY [Member]
Parent [Line Items]
Net current-period other comprehensive income (loss)	0		(107)
Energy Related Derivative [Member] | Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member] | Subsidiaries [Member]
Parent [Line Items]
Net current-period other comprehensive income (loss)	79
Energy Related Derivative [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member] | Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member] | PUGET ENERGY [Member]
Other comprehensive income (loss):
Income tax (benefit) expense	0		(57)
Energy Related Derivative [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member] | Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member] | Subsidiaries [Member]
Other comprehensive income (loss):
Income tax (benefit) expense	0		976
Interest Rate Contract [Member] | Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member] | PUGET ENERGY [Member]
Parent [Line Items]
Net current-period other comprehensive income (loss)	811		2,526
Interest Rate Contract [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member] | Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member] | PUGET ENERGY [Member]
Other comprehensive income (loss):
Income tax (benefit) expense	436		1,360
Interest Rate Contract [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member] | Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member] | Subsidiaries [Member]
Other comprehensive income (loss):
Income tax (benefit) expense	$ 43		$ (129)