CONSOLIDATED STATEMENTS OF COMMON SHAREHOLDER'S EQUITY (USD $) In Thousands, except Share data, unless otherwise specified	Total	Common Stock [Member]	Additional Paid-in Capital [Member]	Earnings Reinvested in the Business [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	PUGET SOUND ENERGY, INC.	PUGET SOUND ENERGY, INC. Common Stock [Member]	PUGET SOUND ENERGY, INC. Additional Paid-in Capital [Member]	PUGET SOUND ENERGY, INC. Earnings Reinvested in the Business [Member]	PUGET SOUND ENERGY, INC. Accumulated Other Comprehensive Income (Loss) [Member]
Balance at Dec. 31, 2009	$ 3,423,468	$ 0	$ 3,308,957	$ 91,024	$ 23,487	$ 3,083,072	$ 859	$ 2,959,205	$ 333,128	$ (210,120)
Balance (in shares) at Dec. 31, 2009		200					85,903,791
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	30,311	0	0	30,311	0	26,095	0	0	26,095	0
Common stock dividend	(104,311)	0	0	(104,311)	0	(186,733)	0	0	(186,733)	0
Other comprehensive income	(26,556)	0	0	0	(26,556)	52,473	0	0	0	52,473
Balance at Dec. 31, 2010	3,322,912	0	3,308,957	17,024	(3,069)	2,974,907	859	2,959,205	172,490	(157,647)
Balance (in shares) at Dec. 31, 2010		200					85,903,791
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	107,431					103,439
Balance at Mar. 31, 2011
Balance at Dec. 31, 2010	3,322,912	0	3,308,957	17,024	(3,069)	2,974,907	859	2,959,205	172,490	(157,647)
Balance (in shares) at Dec. 31, 2010		200					85,903,791
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	123,290	0	0	123,290	0	204,120	0	0	204,120	0
Common stock dividend	(117,441)	0	0	(117,441)	0	(212,875)	0	0	(212,875)	0
Capital Contribution						287,000	0	287,000	0	0
Other comprehensive income	(27,838)	0	0	0	(27,838)	(30,932)	0		0	(30,932)
Balance at Dec. 31, 2011	3,300,923	0	3,308,957	22,873	(30,907)	3,222,220	859	3,246,205	163,735	(188,579)
Balance (in shares) at Dec. 31, 2011		200					85,903,791
Balance at Sep. 30, 2011
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	47,294					58,875
Balance at Dec. 31, 2011	3,300,923					3,222,220
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	88,480					112,716
Balance at Mar. 31, 2012
Balance at Dec. 31, 2011	3,300,923	0	3,308,957	22,873	(30,907)	3,222,220	859	3,246,205	163,735	(188,579)
Balance (in shares) at Dec. 31, 2011		200					85,903,791
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	273,821	0	0	273,821	0	356,170	0	0	356,170	0
Common stock dividend	(88,594)	0	0	(88,594)	0	(175,625)	0	0	(175,625)	0
Capital Contribution						0	0	0	0	0
Other comprehensive income	(1,922)	0	0	0	(1,922)	1,381	0	0	0	1,381
Balance at Dec. 31, 2012	3,484,228	0	3,308,957	208,100	(32,829)	3,404,146	859	3,246,205	344,280	(187,198)
Balance (in shares) at Dec. 31, 2012	200	200				85,903,791	85,903,791
Balance at Sep. 30, 2012
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	80,957					95,714
Balance at Dec. 31, 2012	$ 3,484,228					$ 3,404,146
Balance (in shares) at Dec. 31, 2012	200					85,903,791