Related Party Transactions (Details) (USD $)	12 Months Ended						0 Months Ended			12 Months Ended					12 Months Ended						0 Months Ended					0 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Feb. 10, 2012	Jun. 03, 2011 Contracts	Jun. 03, 2011 interest_rate_swap	Jun. 18, 2012 Co-manager and Underwriter [Member]	Feb. 10, 2012 Co-manager and Underwriter [Member]	Jun. 03, 2011 Co-manager and Underwriter [Member]	Dec. 31, 2012 PUGET SOUND ENERGY, INC.	Dec. 31, 2011 PUGET SOUND ENERGY, INC.	Dec. 31, 2010 PUGET SOUND ENERGY, INC.	Dec. 31, 2012 PUGET SOUND ENERGY, INC. PUGET ENERGY	Dec. 31, 2010 PUGET SOUND ENERGY, INC. PUGET ENERGY	Dec. 31, 2012 PUGET ENERGY	Dec. 31, 2011 PUGET ENERGY	Dec. 31, 2010 PUGET ENERGY	Dec. 31, 2012 Senior secured credit facility PUGET SOUND ENERGY, INC.	Dec. 31, 2012 Senior secured credit facility PUGET SOUND ENERGY, INC. PUGET ENERGY	Dec. 31, 2010 Senior secured credit facility PUGET SOUND ENERGY, INC. PUGET ENERGY	Jun. 03, 2011 Senior Secured Note PUGET ENERGY Co-manager and Underwriter [Member]	Dec. 31, 2012 Senior Secured Note 6.000% Senior Secured Note Due 2021	Dec. 31, 2011 Senior Secured Note 6.000% Senior Secured Note Due 2021	Jun. 03, 2011 Senior Secured Note 6.000% Senior Secured Note Due 2021	Jun. 03, 2011 Senior Secured Note 6.000% Senior Secured Note Due 2021 PUGET ENERGY Co-manager and Underwriter [Member]	Jun. 03, 2011 Term Loan	Feb. 28, 2009 Term Loan	Dec. 31, 2010 Term Loan PUGET ENERGY Co-manager and Underwriter [Member]
Related Party Transaction [Line Items]
Current borrowing capacity of line of credit				$ 1,000,000,000.0						$ 1,150,000,000.00									$ 30,000,000
Debt instrument variable rate basis																		LIBOR	one-month LIBOR
Basis spread on variable rate (percent)																		0.85%	0.25%
Outstanding amount for line of credit													29,600,000	30,000,000
Applicable interest rate on credift facility at period end																			0.50%	1.60%
Long-term debt	5,610,272,000									3,776,272,000	3,773,860,000				1,834,000,000							500,000,000	500,000,000	500,000,000	500,000,000		1,225,000,000	782,000,000
Repayments of long-term debt	1,273,000,000	769,000,000	675,000,000							0	285,000,000	232,000,000			843,000,000	484,000,000	443,000,000				484,000,000					484,000,000
Number of interest rate derivatives held					2	3
Notional amount of interest rate swaps	450,000,000								444,900,000
Notional amount of swap instrument settled	$ 827,400,000						$ 300,000,000	$ 67,500,000	$ 77,400,000