SUPPLEMENTAL QUARTERLY FINANCIAL DATA (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Quarterly Financial Information [Line Items]
Operating revenues	$ 831,165	$ 593,715	$ 662,916	$ 1,025,375	$ 946,645	$ 598,348	$ 642,486	$ 999,818	$ 3,113,171	$ 3,187,297	$ 3,215,156
Operating income	131,215	65,069	145,266	236,301	242,301	100,043	95,081	317,735	577,851	755,160	715,535
Net income (loss)	36,088	(12,958)	41,113	107,592	108,808	8,540	905	167,475	171,835	285,728	273,821
PUGET SOUND ENERGY, INC.
Quarterly Financial Information [Line Items]
Operating revenues	833,881	593,951	662,916	1,025,375	946,794	598,348	642,486	999,707	3,116,123	3,187,335	3,216,259
Operating income	131,214	62,317	142,185	232,977	237,808	96,085	91,094	310,587	568,693	735,574	692,989
Net income (loss)	$ 54,640	$ 3,057	$ 57,834	$ 121,083	$ 122,923	$ 26,605	$ 26,663	$ 179,938	$ 236,614	$ 356,129	$ 356,170