Regulation and Rates (Details) (PUGET SOUND ENERGY, INC. [Member], USD $) In Millions, unless otherwise specified	0 Months Ended
	Nov. 01, 2012	May 14, 2012	May 14, 2012 Electric [Member]	Jun. 28, 2012 Natural Gas [Member]	May 14, 2012 Natural Gas [Member]
Regulatory Assets [Line Items]
Rate Case, Approved Effective Annual Rate Increase			$ 63.3		$ 13.4
Rate Case, Approved Effective Annual Rate Percentage Increase			3.20%		1.30%
Rate Case, Approved Effective Weighted Cost of Capital		7.80%
Rate Case, Approved Effective Common Equity in Capital Structure		48.00%
Rate Case, Approved Effective Return on Equity		9.80%
Accounting Petition, Approved Effective Increase (Decrease) to Revenue				6.9
Accounting Petition, Approved Effective Increase (Decrease) to Conservation Amortization Expense				6.6
Purchased Gas Adjustment, Annual Increase (Decrease) in Revenue	$ 77.0
Purchased Gas Adjustment, Annual Increase (Decrease) in Revenue, Percentage	7.70%