Liquidity Facilities and Other Financing Arrangements (Details) (USD $)									0 Months Ended				12 Months Ended									12 Months Ended			0 Months Ended
	Dec. 31, 2012	Feb. 10, 2012	Dec. 31, 2011	Dec. 31, 2012 Senior secured credit facility	Dec. 31, 2010 Senior secured credit facility	Feb. 10, 2012 Term Loan	Jun. 03, 2011 Term Loan	Dec. 06, 2010 Term Loan	Feb. 10, 2012 Revolving Credit Facility	Dec. 31, 2012 Revolving Credit Facility	Feb. 28, 2009 Capital Expenditure Facility	Feb. 04, 2013 Subsequent Event [Member]	Dec. 31, 2012 PUGET SOUND ENERGY, INC. facility	Dec. 31, 2011 PUGET SOUND ENERGY, INC.	Dec. 31, 2010 PUGET SOUND ENERGY, INC.	Dec. 31, 2012 PUGET SOUND ENERGY, INC. Promissory Note with Puget Energy	Dec. 31, 2010 PUGET SOUND ENERGY, INC. Promissory Note with Puget Energy	Dec. 31, 2012 PUGET SOUND ENERGY, INC. Working Capital Needs	Dec. 31, 2012 PUGET SOUND ENERGY, INC. Capital Expenditure Facility	Dec. 31, 2012 PUGET SOUND ENERGY, INC. Energy Hedging Activities	Dec. 31, 2011 PUGET SOUND ENERGY, INC. Energy Hedging Activities	Dec. 31, 2012 PUGET SOUND ENERGY, INC. Senior secured credit facility	Dec. 31, 2012 PUGET SOUND ENERGY, INC. Senior secured credit facility Promissory Note with Puget Energy	Dec. 31, 2012 PUGET SOUND ENERGY, INC. Letter of Credit Working Capital Needs facility	Feb. 04, 2013 PUGET SOUND ENERGY, INC. Subsequent Event [Member] facility	Feb. 04, 2013 PUGET SOUND ENERGY, INC. Subsequent Event [Member] Working Capital Needs	Feb. 04, 2013 PUGET SOUND ENERGY, INC. Subsequent Event [Member] Energy Hedging Activities	Feb. 04, 2013 PUGET SOUND ENERGY, INC. Subsequent Event [Member] Senior secured credit facility
Short-term Debt [Line Items]
Short-term debt	$ 181,000,000		$ 25,000,000	$ 0	$ 0								$ 181,000,000	$ 25,000,000	$ 25,000,000
Weighted-average interest rate on short-term debt (percent)													6.49%		4.39%
Number of committed unsecured revolving credit facilities													3												2
Current borrowing capacity of line of credit		1,000,000,000.0							1,000,000,000	1,000,000,000.0	1,000,000,000	800,000,000.0	1,150,000,000.00					400,000,000	400,000,000	350,000,000			30,000,000	9,600,000.0	1,000,000,000.0	650,000,000.0	350,000,000.0
Current same-day borrowing capacity													50,000,000												75,000,000.0
Debt instrument variable rate basis																						LIBOR	one-month LIBOR
Basis spread on variable rate (percent)									2.00%													0.85%	0.25%					1.50%
Outstanding amount for line of credit									434,000,000							29,600,000	30,000,000	0	0	350,000,000	0			181,000,000
Number of letter of credit facilities																								2
Outstanding amount letters of credit													4,900,000
Maximum brrowing cpacity												$ 1,300,000,000													$ 1,500,000,000.0
Maximum capitalization percentage																												65.00%
Commitment fee percentage on line of credit													0.26%												0.225%
Term of debt instrument		5 years				5 years	5 years	5 years
Commitment fee percentage for line of credit									0.375%