Accumulated Other Comprehensive Income - Changes by Component (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended		3 Months Ended		9 Months Ended		3 Months Ended	9 Months Ended	3 Months Ended	9 Months Ended	3 Months Ended	9 Months Ended	3 Months Ended	9 Months Ended			3 Months Ended		9 Months Ended		3 Months Ended	9 Months Ended			3 Months Ended	9 Months Ended	3 Months Ended	9 Months Ended	3 Months Ended	9 Months Ended	3 Months Ended	9 Months Ended	3 Months Ended	9 Months Ended	3 Months Ended	9 Months Ended	3 Months Ended	9 Months Ended	3 Months Ended	9 Months Ended	3 Months Ended	9 Months Ended	3 Months Ended	9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013 Interest Rate Contract [Member]	Sep. 30, 2012 Interest Rate Contract [Member]	Sep. 30, 2013 Interest Rate Contract [Member]	Sep. 30, 2012 Interest Rate Contract [Member]	Sep. 30, 2013 PUGET ENERGY [Member]	Sep. 30, 2013 PUGET ENERGY [Member]	Sep. 30, 2013 PUGET ENERGY [Member] Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member] Interest Rate Contract [Member]	Sep. 30, 2013 PUGET ENERGY [Member] Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member] Interest Rate Contract [Member]	Sep. 30, 2013 PUGET ENERGY [Member] Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member] Energy Related Derivative [Member]	Sep. 30, 2013 PUGET ENERGY [Member] Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member] Energy Related Derivative [Member]	Sep. 30, 2013 PUGET ENERGY [Member] Accumulated Defined Benefit Plans Adjustment [Member]	Sep. 30, 2013 PUGET ENERGY [Member] Accumulated Defined Benefit Plans Adjustment [Member]	Jun. 30, 2013 PUGET ENERGY [Member] Accumulated Defined Benefit Plans Adjustment [Member]	Dec. 31, 2012 PUGET ENERGY [Member] Accumulated Defined Benefit Plans Adjustment [Member]	Sep. 30, 2013 Subsidiaries [Member]	Sep. 30, 2012 Subsidiaries [Member]	Sep. 30, 2013 Subsidiaries [Member]	Sep. 30, 2012 Subsidiaries [Member]	Sep. 30, 2013 Subsidiaries [Member] Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member] Interest Rate Contract [Member]	Sep. 30, 2013 Subsidiaries [Member] Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member] Interest Rate Contract [Member]	Jun. 30, 2013 Subsidiaries [Member] Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member] Interest Rate Contract [Member]	Dec. 31, 2012 Subsidiaries [Member] Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member] Interest Rate Contract [Member]	Sep. 30, 2013 Subsidiaries [Member] Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member] Energy Related Derivative [Member]	Sep. 30, 2013 Subsidiaries [Member] Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member] Energy Related Derivative [Member]	Sep. 30, 2013 Subsidiaries [Member] Accumulated Defined Benefit Plans Adjustment [Member]	Sep. 30, 2013 Subsidiaries [Member] Accumulated Defined Benefit Plans Adjustment [Member]	Sep. 30, 2013 Reclassification out of Accumulated Other Comprehensive Income [Member] PUGET ENERGY [Member]	Sep. 30, 2013 Reclassification out of Accumulated Other Comprehensive Income [Member] PUGET ENERGY [Member]	Sep. 30, 2013 Reclassification out of Accumulated Other Comprehensive Income [Member] PUGET ENERGY [Member] Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member] Interest Rate Contract [Member]	Sep. 30, 2013 Reclassification out of Accumulated Other Comprehensive Income [Member] PUGET ENERGY [Member] Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member] Interest Rate Contract [Member]	Sep. 30, 2013 Reclassification out of Accumulated Other Comprehensive Income [Member] PUGET ENERGY [Member] Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member] Energy Related Derivative [Member]	Sep. 30, 2013 Reclassification out of Accumulated Other Comprehensive Income [Member] PUGET ENERGY [Member] Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member] Energy Related Derivative [Member]	Sep. 30, 2013 Reclassification out of Accumulated Other Comprehensive Income [Member] PUGET ENERGY [Member] Accumulated Defined Benefit Plans Adjustment [Member]	Sep. 30, 2013 Reclassification out of Accumulated Other Comprehensive Income [Member] PUGET ENERGY [Member] Accumulated Defined Benefit Plans Adjustment [Member]	Sep. 30, 2013 Reclassification out of Accumulated Other Comprehensive Income [Member] Subsidiaries [Member]	Sep. 30, 2013 Reclassification out of Accumulated Other Comprehensive Income [Member] Subsidiaries [Member]	Sep. 30, 2013 Reclassification out of Accumulated Other Comprehensive Income [Member] Subsidiaries [Member] Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member] Interest Rate Contract [Member]	Sep. 30, 2013 Reclassification out of Accumulated Other Comprehensive Income [Member] Subsidiaries [Member] Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member] Interest Rate Contract [Member]	Sep. 30, 2013 Reclassification out of Accumulated Other Comprehensive Income [Member] Subsidiaries [Member] Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member] Energy Related Derivative [Member]	Sep. 30, 2013 Reclassification out of Accumulated Other Comprehensive Income [Member] Subsidiaries [Member] Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member] Energy Related Derivative [Member]	Sep. 30, 2013 Reclassification out of Accumulated Other Comprehensive Income [Member] Subsidiaries [Member] Accumulated Defined Benefit Plans Adjustment [Member]	Sep. 30, 2013 Reclassification out of Accumulated Other Comprehensive Income [Member] Subsidiaries [Member] Accumulated Defined Benefit Plans Adjustment [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans, Net of Tax																	$ (29,825)	$ (29,065)							$ (170,733)	$ (175,998)
Income tax (benefit) expense	5,936	20,943	75,569	73,289															14,530	30,949	105,470	108,250											436	1,360	0	(57)	(212)	(636)			43	(129)	0	976	(1,834)	(5,501)
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning of Period			(32,829)						(31,981)	(32,829)	(1,307)	(3,022)	(849)	(742)					(179,964)		(187,198)						(6,466)	(6,624)	(2,765)	(4,576)
Other comprehensive income (loss) before reclassifications									0	(1,548)	0	0	0	0	0	(1,548)			0		(1,548)		0	(1,548)			0	0	0	0
Other Comprehensive Income Reclassification Of Net Unrealized Gain Loss On Interest Rate Swaps During Period Net Of Tax					(811)	(1,055)	(2,526)	(10,651)
Amounts reclassified from accumulated other comprehensive income (loss), net of tax									1,204	3,600					393	1,181			3,485		12,267		3,406	(10,219)
Other Comprehensive Income (Loss), Reclassification Adjustment on Derivatives Included in Net Income, Net of Tax	0	255	(107)	182															0	1,456	1,811	6,247
Amortization Of Financing Cash Flow Hedge Contracts To Earnings During Period Net Of Tax																			79	79	237	238
Net current-period other comprehensive income (loss)									1,204	2,052	811	2,526	0	(107)					3,485		10,719						79
End of Period	(30,777)		(30,777)						(30,777)	(30,777)	(496)	(496)	(849)	(849)	(29,432)	(29,432)			(176,479)		(176,479)		(167,327)	(167,327)			(6,387)	(6,387)	(2,765)	(2,765)
Net income (loss)	$ 8,540	$ 46,692	$ 176,919	$ 192,863															$ 26,605	$ 66,868	$ 233,205	$ 260,456									$ (1,204)	$ (3,600)	$ (811)	$ (2,526)	$ 0	$ 107	$ (393)	$ (1,181)	$ (3,485)	$ (12,266)	$ (79)	$ (237)		$ (1,810)	$ (3,406)	$ (10,219)