CONSOLIDATED BALANCE SHEETS (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Utility plant (at original cost, including construction work in progress):
Electric plant	$ 6,808,468	$ 6,750,400
Gas plant	2,419,175	2,385,784
Common plant	494,079	487,931
Less: Accumulated depreciation and amortization	(1,128,946)	(1,067,424)
Net utility plant	8,592,776	8,556,691
Other property and investments:
Goodwill	1,656,513	1,656,513
Other property and investments	103,922	112,367
Total other property and investments	1,760,435	1,768,880
Current assets:
Cash and cash equivalents	113,988	135,542
Restricted cash	3,101	3,700
Accounts receivable, net of allowance for doubtful accounts	322,299	321,480
Unbilled revenue	172,039	204,359
Materials and supplies, at average cost	80,526	82,353
Fuel and gas inventory, at average cost	61,851	88,953
Derivative Assets, Current	20,410	6,869
Income taxes	4,648	4,796
Prepaid expense and other	17,271	13,571
Power contract acquisition adjustment gain	50,346	50,785
Deferred income taxes	16,241	53,437
Total current assets	862,720	965,845
Other long-term and regulatory assets:
Regulatory asset for deferred income taxes	129,951	119,844
Power cost adjustment mechanism	3,795	3,773
Regulatory assets related to power contracts	36,928	37,655
Other regulatory assets	743,189	815,785
Unrealized gain on derivative instruments	14,452	14,814
Power contract acquisition adjustment gain	441,297	456,225
Other	99,475	95,763
Total other long-term and regulatory assets	1,469,087	1,543,859
Total assets	12,685,018	12,835,275
Capitalization:
Common stock	0	0
Additional paid-in capital	3,308,957	3,308,957
Earnings reinvested in the business	333,504	208,100
Accumulated other comprehensive income (loss), net of tax	(31,735)	(32,829)
Total common shareholder's equity	3,610,726	3,484,228
Long-term debt:
First mortgage bonds and senior notes	3,351,412	3,351,412
Pollution control bonds	161,860	161,860
Junior subordinated notes	250,000	250,000
Long-term debt	1,805,000	1,834,000
Debt discount and other	(260,995)	(264,072)
Total long-term debt	5,307,277	5,333,200
Total capitalization	8,918,003	8,817,428
Current liabilities:
Accounts payable	266,714	321,755
Short-term debt	25,000	181,000
Long-term Debt, Current Maturities	13,000	13,000
Purchased gas adjustment liability	26,869	32,587
Accrued expenses:
Taxes	112,369	95,623
Salaries and wages	27,579	38,438
Interest	74,939	82,262
Derivative Liabilities, Current	81,198	177,519
Power contract acquisition adjustment loss	3,943	3,902
Other	89,817	72,799
Total current liabilities	721,428	1,018,885
Long-term and regulatory liabilities:
Deferred income taxes	1,305,727	1,261,636
Unrealized loss on derivative instruments	51,987	83,276
Regulatory liabilities	645,158	600,697
Regulatory liabilities related to power contracts	491,643	507,009
Power contract acquisition adjustment loss	32,985	33,753
Other deferred credits	518,087	512,591
Total long-term and regulatory liabilities	3,045,587	2,998,962
Commitments and contingencies
Total capitalization and liabilities	12,685,018	12,835,275
PUGET SOUND ENERGY, INC. [Member]
Utility plant (at original cost, including construction work in progress):
Electric plant	9,077,027	9,048,356
Gas plant	3,030,835	2,998,188
Common plant	557,500	555,549
Less: Accumulated depreciation and amortization	(4,072,586)	(4,045,402)
Net utility plant	8,592,776	8,556,691
Other property and investments:
Other property and investments	95,091	103,646
Total other property and investments	95,091	103,646
Current assets:
Cash and cash equivalents	113,947	135,530
Restricted cash	3,101	3,700
Accounts receivable, net of allowance for doubtful accounts	322,739	321,685
Unbilled revenue	172,039	204,359
Materials and supplies, at average cost	80,526	82,353
Fuel and gas inventory, at average cost	58,450	85,547
Derivative Assets, Current	20,410	6,869
Income taxes	4,648	4,796
Prepaid expense and other	17,145	13,413
Deferred income taxes	30,956	68,015
Total current assets	823,961	926,267
Other long-term and regulatory assets:
Regulatory asset for deferred income taxes	129,386	119,279
Power cost adjustment mechanism	3,795	3,773
Other regulatory assets	741,359	813,171
Unrealized gain on derivative instruments	14,452	14,814
Other	94,558	90,330
Total other long-term and regulatory assets	983,550	1,041,367
Total assets	10,495,378	10,627,971
Capitalization:
Common stock	859	859
Additional paid-in capital	3,246,205	3,246,205
Earnings reinvested in the business	418,569	344,280
Accumulated other comprehensive income (loss), net of tax	(181,922)	(187,198)
Total common shareholder's equity	3,483,711	3,404,146
Long-term debt:
First mortgage bonds and senior notes	3,351,412	3,351,412
Pollution control bonds	161,860	161,860
Junior subordinated notes	250,000	250,000
Debt discount and other	(14)	(14)
Total long-term debt	3,763,258	3,763,258
Total capitalization	7,246,969	7,167,404
Current liabilities:
Accounts payable	267,126	321,953
Short-term debt	25,000	181,000
Short-term note owed to parent	29,598	29,598
Long-term Debt, Current Maturities	13,000	13,000
Purchased gas adjustment liability	26,869	32,587
Accrued expenses:
Taxes	112,369	95,623
Salaries and wages	27,579	38,438
Interest	57,274	55,806
Derivative Liabilities, Current	74,652	170,948
Other	87,548	69,881
Total current liabilities	721,015	1,008,834
Long-term and regulatory liabilities:
Deferred income taxes	1,330,252	1,274,602
Unrealized loss on derivative instruments	38,567	68,323
Regulatory liabilities	641,011	596,324
Other deferred credits	517,564	512,484
Total long-term and regulatory liabilities	2,527,394	2,451,733
Commitments and contingencies
Total capitalization and liabilities	$ 10,495,378	$ 10,627,971