CONSOLIDATED BALANCE SHEETS (USD $) In Thousands, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010
Utility plant:
Electric plant	$ 6,067,672	$ 5,253,786
Gas plant	2,238,741	2,129,200
Common plant	418,236	318,615
Less: Accumulated depreciation and amortization	(674,782)	(429,038)
Net utility plant	8,049,867	7,272,563
Other property and investments:
Goodwill	1,656,513	1,656,513
Investment in exchange power contract	19,396	22,923
Other property and investments	123,352	125,918
Total other property and investments	1,799,261	1,805,354
Current assets:
Cash and cash equivalents	37,235	36,557
Restricted cash	4,183	5,470
Accounts receivable, net of allowance for doubtful accounts	336,530	327,615
Unbilled revenue	191,150	194,088
Purchased gas adjustment receivable	0	5,992
Materials and supplies, at average cost	76,068	85,413
Fuel and gas inventory, at average cost	100,491	96,633
Unrealized gain on derivative instruments	6,647	7,500
Income taxes	11,553	76,183
Prepaid expense and other	13,969	14,835
Power contract acquisition adjustment gain	65,096	134,553
Deferred income taxes	101,934	83,086
Total current assets	944,856	1,067,925
Other long-term and regulatory assets:
Regulatory asset for deferred income taxes	62,304	73,337
Power cost adjustment mechanism	6,818	15,618
Regulatory assets related to power contracts	46,202	116,116
Other regulatory assets	766,825	814,603
Unrealized gain on derivative instruments	10,084	8,233
Power contract acquisition adjustment gain	517,740	624,667
Other	180,753	130,920
Total other long-term and regulatory assets	1,590,726	1,783,494
Total assets	12,384,710	11,929,336
Common shareholder's equity:
Common stock	0	0
Additional paid-in capital	3,308,957	3,308,957
Earnings reinvested in the business	22,873	17,024
Accumulated other comprehensive income (loss), net of tax	(30,907)	(3,069)
Total common shareholder's equity	3,300,923	3,322,912
Long-term debt:
First mortgage bonds and senior notes	3,362,000	2,792,000
Pollution control bonds	161,860	161,860
Junior subordinated notes	250,000	250,000
Long-term debt	1,793,000	1,490,000
Debt discount and other	(289,493)	(311,147)
Total long-term debt	5,277,367	4,382,713
Total capitalization	8,578,290	7,705,625
Current liabilities:
Accounts payable	339,361	291,148
Short-term debt	25,000	247,000
Current maturities of long-term debt	0	260,000
Purchased gas adjustment liability	25,940	0
Accrued expenses:
Taxes	90,727	81,505
Salaries and wages	40,892	34,453
Interest	69,329	59,182
Unrealized loss on derivative instruments	327,089	273,100
Power contract acquisition adjustment loss	8,547	69,915
Other	74,409	114,409
Total current liabilities	1,001,294	1,430,712
Long-term and regulatory liabilities:
Deferred income taxes	1,153,755	1,127,611
Unrealized loss on derivative instruments	196,558	183,135
Regulatory liabilities	346,225	305,936
Regulatory liabilities related to power contracts	582,836	759,220
Power contract acquisition adjustment loss	37,655	46,779
Other deferred credits	488,097	370,318
Total long-term and regulatory liabilities	2,805,126	2,792,999
Commitments and contingencies (Note 19)
Total capitalization and liabilities	12,384,710	11,929,336
PUGET SOUND ENERGY, INC. [Member]
Utility plant:
Electric plant	8,390,667	7,586,208
Gas plant	2,855,794	2,752,962
Common plant	518,318	427,227
Less: Accumulated depreciation and amortization	(3,714,912)	(3,509,277)
Net utility plant	8,049,867	7,257,120
Other property and investments:
Investment in exchange power contract	19,396	22,923
Other property and investments	113,528	115,056
Total other property and investments	132,924	137,979
Current assets:
Cash and cash equivalents	31,010	36,320
Restricted cash	4,183	5,470
Accounts receivable, net of allowance for doubtful accounts	336,483	327,341
Unbilled revenue	191,150	194,088
Purchased gas adjustment receivable	0	5,992
Materials and supplies, at average cost	76,068	84,222
Fuel and gas inventory, at average cost	97,074	92,222
Unrealized gain on derivative instruments	6,647	7,500
Income taxes	11,553	62,114
Prepaid expense and other	13,807	14,412
Deferred income taxes	112,204	80,215
Total current assets	880,179	909,896
Other long-term and regulatory assets:
Regulatory asset for deferred income taxes	61,344	73,337
Power cost adjustment mechanism	6,818	15,618
Other regulatory assets	760,585	769,744
Unrealized gain on derivative instruments	10,084	8,233
Other	183,746	138,857
Total other long-term and regulatory assets	1,022,577	1,005,789
Total assets	10,085,547	9,310,784
Common shareholder's equity:
Common stock	859	859
Additional paid-in capital	3,246,205	2,959,205
Earnings reinvested in the business	163,735	172,490
Accumulated other comprehensive income (loss), net of tax	(188,579)	(157,647)
Total common shareholder's equity	3,222,220	2,974,907
Long-term debt:
First mortgage bonds and senior notes	3,362,000	2,792,000
Pollution control bonds	161,860	161,860
Junior subordinated notes	250,000	250,000
Debt discount and other	(15)	0
Total long-term debt	3,773,845	3,203,860
Total capitalization	6,996,065	6,178,767
Current liabilities:
Accounts payable	339,568	291,765
Short-term debt	25,000	247,000
Short-term note owed to parent	29,998	22,598
Current maturities of long-term debt	0	260,000
Purchased gas adjustment liability	25,940	0
Accrued expenses:
Taxes	90,727	81,505
Salaries and wages	40,892	34,453
Interest	55,843	54,723
Unrealized loss on derivative instruments	301,879	243,053
Other	68,346	49,661
Total current liabilities	978,193	1,284,758
Long-term and regulatory liabilities:
Deferred income taxes	1,115,639	1,034,517
Unrealized loss on derivative instruments	169,359	155,179
Regulatory liabilities	340,907	296,884
Other deferred credits	485,384	360,679
Total long-term and regulatory liabilities	2,111,289	1,847,259
Commitments and contingencies (Note 19)
Total capitalization and liabilities	$ 10,085,547	$ 9,310,784