Dividend Payment Restrictions (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012
Parent [Line Items]
Retained Earnings, Unappropriated	$ 551.7
Dividends, Earnings Before Interest, Tax, Deprecation and Amortization Ratio, Threshold For Dividend Payment	2
Dividends, Earnings Before Interest, Tax, Deprecation and Amortization Ratio at Period End	2.7
PUGET SOUND ENERGY, INC.
Parent [Line Items]
Dividends, Common Equity Ratio, Threshold For Dividend Payment	44.00%
Dividends, Earnings Before Interest, Tax, Deprecation and Amortization Ratio, Threshold For Dividend Payment	3
Dividends, Common Equity Ratio at Period End	48.00%
Dividends, Earnings Before Interest, Tax, Deprecation and Amortization Ratio at Period End	4.5