Regulation and Rates Rate Adjustments (Details) (PUGET SOUND ENERGY, INC., USD $) In Millions, unless otherwise specified						12 Months Ended
	May 07, 2012 Electric	Apr. 02, 2010 Electric	Dec. 31, 2012 Electric April 8, 2010 [Member]	Dec. 31, 2012 Electric November 1, 2011 Through March 31, 2011 [Member]	Dec. 31, 2012 Electric May 14, 2012 [Member]	Dec. 31, 2012 Gas November 1, 2012 [Member]	Dec. 31, 2012 Gas April 8, 2010 [Member]	Dec. 31, 2012 Gas May 14, 2012 [Member]	Dec. 31, 2012 Gas November 1, 2011 [Member]	Dec. 31, 2012 Gas April 1, 2011 [Member]	Dec. 31, 2012 Gas November 1, 2010 Through October 31, 2011 [Member]	Dec. 31, 2012 Gas October 1, 2009 Through October 31, 2010 [Member]	Dec. 31, 2012 Gas June 1, 2009 [Member]
Regulation and Rates [Line Items]
Average Percentage Increase (Decrease) in Rates	3.20%	3.70%	3.70%	(2.90%)	3.20%
Increase (Decrease) in Revenue	$ 63.3	$ 74.1	$ 74.1	$ (27.7)	$ 63.3
Average Percentage Increase (Decrease) in Rates						(7.70%)	0.80%	1.30%	(4.30%)	1.80%	1.90%	(17.10%)	(1.80%)
Increase (Decrease) in Revenue						$ (77.0)	$ 10.1	$ 13.4	$ (43.5)	$ 19.0	$ 18.3	$ (198.1)	$ (21.2)