Accumulated Other Comprehensive Income - Changes by Component (Details) (USD $) In Thousands, unless otherwise specified			3 Months Ended
	Mar. 31, 2013	Dec. 31, 2012	Mar. 31, 2013 PUGET ENERGY [Member]	Mar. 31, 2013 PUGET ENERGY [Member] Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member] Interest Rate Contract [Member]	Mar. 31, 2013 PUGET ENERGY [Member] Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member] Energy Related Derivative [Member]	Mar. 31, 2013 PUGET ENERGY [Member] Accumulated Defined Benefit Plans Adjustment [Member]	Mar. 31, 2013 PUGET SOUND ENERGY, INC. [Member]	Mar. 31, 2013 PUGET SOUND ENERGY, INC. [Member] Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member] Interest Rate Contract [Member]	Mar. 31, 2013 PUGET SOUND ENERGY, INC. [Member] Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member] Energy Related Derivative [Member]	Mar. 31, 2013 PUGET SOUND ENERGY, INC. [Member] Accumulated Defined Benefit Plans Adjustment [Member]
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Balance at December 31, 2012	$ (31,735)	$ (32,829)		$ (3,022)	$ (742)	$ (29,065)	$ (187,198)	$ (175,998)	$ (6,624)	$ (4,576)
Other comprehensive income (loss) before reclassifications			0	0	0	0	0	0	0	0
Amounts reclassified from accumulated other comprehensive income (loss), net of tax			1,094	854	(107)	347	5,276	3,386	79	1,811
Net current-period other comprehensive income (loss)			1,094	854	(107)	347	5,276	3,386	79	1,811
Balance at March 31, 2013	$ (31,735)	$ (32,829)		$ (2,168)	$ (849)	$ (28,718)	$ (181,922)	$ (172,612)	$ (6,545)	$ (2,765)