Segment Information (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2012 segment	Dec. 31, 2011	Dec. 31, 2010
Segment Reporting Information [Line Items]
Number of operating segments									1
Revenue	$ 909,272	$ 578,755	$ 678,617	$ 1,048,512	$ 968,721	$ 597,776	$ 732,675	$ 1,019,593	$ 3,215,156	$ 3,318,765	$ 3,122,217
Depreciation and amortization									393,771	371,978	364,206
Income tax (benefit) expense									104,725	33,760	2,481
Operating income	193,374	153,262	159,876	209,023	121,439	20,663	114,693	218,145	715,535	474,940	308,234
Interest charges, net of AFUDC									370,000	341,961	307,010
Net income	80,957	46,692	57,692	88,480	47,294	(36,470)	5,035	107,431	273,821	123,290	30,311
Total assets	12,801,579				12,407,306				12,801,579	12,407,306	11,958,011
Construction expenditures - excluding equity AFUDC									859,791	976,513	859,091
Regulated Utility
Segment Reporting Information [Line Items]
Revenue									3,215,876	3,319,105	3,121,934
Depreciation and amortization									393,770	371,977	364,205
Income tax (benefit) expense									154,805	91,464	35,905
Operating income									718,622	477,730	310,130
Interest charges, net of AFUDC									234,890	210,463	220,922
Net income									366,377	228,908	92,927
Total assets	11,076,350				10,671,089				11,076,350	10,671,089	10,209,207
Construction expenditures - excluding equity AFUDC									859,791	976,513	859,091
Other
Segment Reporting Information [Line Items]
Revenue									(720)	(340)	283
Depreciation and amortization									1	1	1
Income tax (benefit) expense									(50,080)	(57,704)	(33,424)
Operating income									(3,087)	(2,790)	(1,896)
Interest charges, net of AFUDC									135,110	131,498	86,088
Net income									(92,556)	(105,618)	(62,616)
Total assets	1,725,229				1,736,217				1,725,229	1,736,217	1,748,804
Construction expenditures - excluding equity AFUDC									0	0	0
PUGET SOUND ENERGY, INC.
Segment Reporting Information [Line Items]
Area of service territory (sqmi)	6,000								6,000
Number of subsidiaries									2
Revenue	909,519	579,611	678,617	1,048,512	969,070	597,776	733,364	1,019,593	3,216,259	3,319,803	3,122,217
Depreciation and amortization									393,771	371,978	364,206
Income tax (benefit) expense									149,308	78,117	122
Operating income	188,431	150,007	153,306	201,245	116,029	17,198	107,380	190,436	692,989	431,043	207,591
Interest charges, net of AFUDC									224,797	201,467	220,854
Net income	95,714	66,868	80,872	112,716	58,875	(9,107)	50,913	103,439	356,170	204,120	26,095
Total assets	10,594,276				10,108,143				10,594,276	10,108,143	9,339,459
Construction expenditures - excluding equity AFUDC									859,791	976,513	859,091
PUGET SOUND ENERGY, INC. | Regulated Utility
Segment Reporting Information [Line Items]
Revenue									3,215,876	3,319,106	3,121,935
Depreciation and amortization									393,770	371,977	364,204
Income tax (benefit) expense									149,731	78,451	60
Operating income									694,035	431,553	207,647
Interest charges, net of AFUDC									224,797	201,467	220,854
Net income									356,956	204,740	26,358
Total assets	10,555,289				10,064,859				10,555,289	10,064,859	9,289,350
Construction expenditures - excluding equity AFUDC									859,791	976,513	859,091
PUGET SOUND ENERGY, INC. | Other
Segment Reporting Information [Line Items]
Revenue									383	697	282
Depreciation and amortization									1	1	2
Income tax (benefit) expense									(423)	(334)	62
Operating income									(1,046)	(510)	(56)
Interest charges, net of AFUDC									0	0	0
Net income									(786)	(620)	(263)
Total assets	38,987				43,284				38,987	43,284	50,109
Construction expenditures - excluding equity AFUDC									$ 0	$ 0	$ 0