Summary of Significant Accounting Policies - AFUDC (Details) (USD $) In Thousands, unless otherwise specified	0 Months Ended	8 Months Ended	12 Months Ended			25 Months Ended
	Nov. 01, 2008	Dec. 31, 2012	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	May 13, 2012
Regulatory Assets [Line Items]
Washington Commission AFUDC Rates	8.25%	7.80%				8.10%
Debt AFUDC			$ 22,216	$ 29,949	$ 14,157
PUGET SOUND ENERGY, INC.
Regulatory Assets [Line Items]
Equity AFUDC			25,469	32,431	12,677
Washington Commission AFUDC			1,895	5,108	3,715
Total in other income			27,364	37,539	16,392
Debt AFUDC			22,216	29,949	14,157
Total AFUDC			$ 49,580	$ 67,488	$ 30,549