Accumulated Other Comprehensive Income - Reclassification Location (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Reclassification out of Accumulated Other Comprehensive Income [Line Items]
Interest expense	$ (108,917)	$ (95,964)	$ (204,733)	$ (203,165)
Purchased electricity	112,543	156,098	287,587	355,213
Income (loss) before income taxes	(52)	77,692	238,014	198,517
Net income (loss)	905	57,692	168,380	146,171
Income Tax Expense (Benefit)	957	(20,000)	(69,634)	(52,346)
Subsidiaries [Member]
Reclassification out of Accumulated Other Comprehensive Income [Line Items]
Interest expense	(65,773)	(62,333)	(131,749)	(123,071)
Purchased electricity	112,543	156,098	287,587	355,213
Income (loss) before income taxes	37,843	111,959	297,542	270,889
Net income (loss)	26,663	80,872	206,601	193,588
Income Tax Expense (Benefit)	(11,180)	(31,087)	(90,941)	(77,301)
Subsidiaries [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification out of Accumulated Other Comprehensive Income [Line Items]
Net income (loss)	(3,506)		(8,782)
Subsidiaries [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		781
Amortization of net gain (loss)	(5,661)		(11,260)
Income (loss) before income taxes	(5,272)		(10,479)
Net income (loss)	(3,427)		(6,813)
Income Tax Expense (Benefit)	1,845		3,666
Subsidiaries [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	0		(2,786)
Net income (loss)			(1,811)
Income Tax Expense (Benefit)	0		975
Subsidiaries [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		244
Net income (loss)	(79)		(158)
Income Tax Expense (Benefit)	43		86
PUGET ENERGY [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification out of Accumulated Other Comprehensive Income [Line Items]
Net income (loss)	(1,302)		(2,396)
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		999
Amortization of net gain (loss)	(1,177)		(2,209)
Income (loss) before income taxes	(678)		(1,210)
Net income (loss)	(441)		(788)
Income Tax Expense (Benefit)	237		422
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	0		164
Net income (loss)	0		107
Income Tax Expense (Benefit)	0		(57)
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	1,325		2,639
Net income (loss)	(861)		(1,715)
Income Tax Expense (Benefit)	$ 464		$ 924