Accumulated Other Comprehensive Income - Reclassification Location (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013		Mar. 31, 2012
Reclassification out of Accumulated Other Comprehensive Income [Line Items]
Interest expense	$ 95,816		$ 107,201
Purchased electricity	175,043		199,115
Total before tax	238,065		120,827
Income tax (expense) benefit	(70,590)		(32,347)
Net of Tax	167,475		88,480
PUGET SOUND ENERGY, INC. [Member]
Reclassification out of Accumulated Other Comprehensive Income [Line Items]
Interest expense	65,977		60,737
Purchased electricity	175,043		199,115
Total before tax	259,699		158,931
Income tax (expense) benefit	(79,761)		(46,215)
Net of Tax	179,938		112,716
PUGET SOUND ENERGY, INC. [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification out of Accumulated Other Comprehensive Income [Line Items]
Net of Tax	(5,276)
PUGET SOUND ENERGY, INC. [Member] | Accumulated Defined Benefit Plans Adjustment [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification out of Accumulated Other Comprehensive Income [Line Items]
Amortization of prior service cost	389	[1]
Amortization of net gain (loss)	(5,599)	[1]
Total before tax	(5,210)
Income tax (expense) benefit	1,824
Net of Tax	(3,386)
PUGET SOUND ENERGY, INC. [Member] | Energy Related Derivative [Member] | Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification out of Accumulated Other Comprehensive Income [Line Items]
Purchased electricity	(2,786)
Income tax (expense) benefit	975
Net of Tax	(1,811)
PUGET SOUND ENERGY, INC. [Member] | Interest Rate Contract [Member] | Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification out of Accumulated Other Comprehensive Income [Line Items]
Interest expense	(122)
Income tax (expense) benefit	43
Net of Tax	(79)
PUGET ENERGY [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification out of Accumulated Other Comprehensive Income [Line Items]
Net of Tax	(1,094)
PUGET ENERGY [Member] | Accumulated Defined Benefit Plans Adjustment [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification out of Accumulated Other Comprehensive Income [Line Items]
Amortization of prior service cost	499	[1]
Amortization of net gain (loss)	(1,032)	[1]
Total before tax	(533)
Income tax (expense) benefit	186
Net of Tax	(347)
PUGET ENERGY [Member] | Energy Related Derivative [Member] | Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification out of Accumulated Other Comprehensive Income [Line Items]
Purchased electricity	164
Income tax (expense) benefit	(57)
Net of Tax	107
PUGET ENERGY [Member] | Interest Rate Contract [Member] | Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification out of Accumulated Other Comprehensive Income [Line Items]
Interest expense	(1,314)
Income tax (expense) benefit	460
Net of Tax	$ (854)

[1] These accumulated other comprehensive income components are included in the computation of net periodic pension cost (see Note 5 for additional details).