Regulation and Rates (Details) (USD $)	12 Months Ended			7 Months Ended	11 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Jan. 31, 2013	Dec. 31, 2013	Feb. 28, 2012 MW	Nov. 09, 2009 MW	Nov. 08, 2009 MW	Dec. 22, 2009
Regulation and Rates [Line Items]
Public Utilities, Rate Case, Deferred Storm Costs Threshold	$ 8,000,000
Facility Power Capacity						343	273	229
Accrual for Environmental Loss Contingencies	25,200,000
Electric
Regulation and Rates [Line Items]
Environmental Exit Costs, Reasonably Possible Additional Losses, Low Estimate	5,700,000
Environmental Expense and Liabilities	13,400,000	12,300,000	10,900,000
Gas plant
Regulation and Rates [Line Items]
Environmental Exit Costs, Reasonably Possible Additional Losses, Low Estimate	35,400,000
Environmental Expense and Liabilities	52,600,000	45,100,000	66,400,000
PUGET SOUND ENERGY, INC.
Regulation and Rates [Line Items]
Regulatory Liabilities Reclassified from Accumulated Depreciation	313,100,000	269,500,000
Storm Damage Costs Incurred During Period	29,700,000	9,400,000
Storm Damage Costs Deferred During Period	18,000,000	0
American Recovery and Reinvestment Tax Act of 2009, Grant Approved Amount			205,300,000						28,700,000
American Recovery and Reinvestment Tax Act of 2009, Grant, Amortization Period Included in Customer Pass Through					11 months
American Recovery and Reinvestment Tax Act of 2009, Grant, Overall Average Rate Reduction	(0.26%)				2.76%
American Recovery and Reinvestment Tax Act of 2009, Total Grant Pass Through Amount	58,500,000
American Recovery and Reinvestment Tax Act of 2009, Grant, Approved Pass Back Rate			0.1
American Recovery and Reinvestment Tax Act of 2009, Grant Amortization Period					10 years
American Recovery and Reinvestment Tax Act of 2009, Grant Pass Through Amount	37,800,000				34,600,000
American Recovery and Reinvestment Tax Act of 2009, Grant Pass Through Interest Amount	$ 20,600,000			$ 2,400,000	$ 23,800,000
Requlatory Assets Related to Power Contracts | Parent Company [Member]
Regulation and Rates [Line Items]
Net Regulatory Assets, Remaining Amortization Period, Min	1 year
Net Regulatory Assets, Remaining Amortization Period, Max	22 years
Chelan PUD contract initiation | PUGET SOUND ENERGY, INC.
Regulation and Rates [Line Items]
Net Regulatory Assets, Remaining Amortization Period	16 years 9 months 18 days
Snoqualmie | PUGET SOUND ENERGY, INC.
Regulation and Rates [Line Items]
Net Regulatory Assets, Remaining Amortization Period	3 years 9 months
PGA receivable [Domain] | PUGET SOUND ENERGY, INC.
Regulation and Rates [Line Items]
Net Regulatory Assets, Remaining Amortization Period	1 year
Electron Unrecovered Loss | PUGET SOUND ENERGY, INC.
Regulation and Rates [Line Items]
Net Regulatory Assets, Remaining Amortization Period	4 years
White River relicensing and other costs | PUGET SOUND ENERGY, INC.
Regulation and Rates [Line Items]
Net Regulatory Assets, Remaining Amortization Period	17 years 10 months 24 days
Baker Dam Licensing Operating Maintenance Costs [Member] | PUGET SOUND ENERGY, INC.
Regulation and Rates [Line Items]
Net Regulatory Assets, Remaining Amortization Period	44 years
Storm damage costs electric | PUGET SOUND ENERGY, INC.
Regulation and Rates [Line Items]
Net Regulatory Assets, Remaining Amortization Period, Min	1 year
Net Regulatory Assets, Remaining Amortization Period, Max	4 years
Colstrip common property | PUGET SOUND ENERGY, INC.
Regulation and Rates [Line Items]
Net Regulatory Assets, Remaining Amortization Period	9 years 6 months
Snoqualmie Licensing Operating Maintenance Costs | PUGET SOUND ENERGY, INC.
Regulation and Rates [Line Items]
Net Regulatory Assets, Remaining Amortization Period	30 years
Deferred Washington Commission AFUDC | PUGET SOUND ENERGY, INC.
Regulation and Rates [Line Items]
Net Regulatory Assets, Remaining Amortization Period, Max	35 years
Energy Conservation Costs [Member] | PUGET SOUND ENERGY, INC.
Regulation and Rates [Line Items]
Net Regulatory Assets, Remaining Amortization Period, Min	1 year
Net Regulatory Assets, Remaining Amortization Period, Max	2 years
Unamortized loss on reacquired debt | PUGET SOUND ENERGY, INC.
Regulation and Rates [Line Items]
Net Regulatory Assets, Remaining Amortization Period, Min	1 year
Net Regulatory Assets, Remaining Amortization Period, Max	21 years 6 months
Mint Farm ownership and operating costs | PUGET SOUND ENERGY, INC.
Regulation and Rates [Line Items]
Net Regulatory Assets, Remaining Amortization Period	10 years 3 months 18 days
Ferndale | PUGET SOUND ENERGY, INC.
Regulation and Rates [Line Items]
Net Regulatory Assets, Remaining Amortization Period	4 years 9 months 18 days
Investment in Bonneville Exchange power contract | PUGET SOUND ENERGY, INC.
Regulation and Rates [Line Items]
Net Regulatory Assets, Remaining Amortization Period	2 years 6 months
Lower Snake River | PUGET SOUND ENERGY, INC.
Regulation and Rates [Line Items]
Net Regulatory Assets, Remaining Amortization Period, Min	1 year 4 months
Net Regulatory Assets, Remaining Amortization Period, Max	22 years 4 months
Regulatory liabilities related to power contracts | Parent Company [Member]
Regulation and Rates [Line Items]
Net Regulatory Assets, Remaining Amortization Period, Min	1 year
Net Regulatory Assets, Remaining Amortization Period, Max	37 years
Renewable energy credits | PUGET SOUND ENERGY, INC.
Regulation and Rates [Line Items]
Net Regulatory Assets, Remaining Amortization Period	1 year
Deferred credit on Biogas sale | PUGET SOUND ENERGY, INC.
Regulation and Rates [Line Items]
Net Regulatory Assets, Remaining Amortization Period	1 year
Deferred credit on gas pipeline capacity | PUGET SOUND ENERGY, INC.
Regulation and Rates [Line Items]
Net Regulatory Assets, Remaining Amortization Period, Max	3 years 9 months 18 days
Decoupling over-collection | PUGET SOUND ENERGY, INC.
Regulation and Rates [Line Items]
Net Regulatory Assets, Remaining Amortization Period	2 years
Summit purchase option buy-out | PUGET SOUND ENERGY, INC.
Regulation and Rates [Line Items]
Net Regulatory Assets, Remaining Amortization Period	5 years 9 months 18 days
Treasury grants | PUGET SOUND ENERGY, INC.
Regulation and Rates [Line Items]
Net Regulatory Assets, Remaining Amortization Period, Min	5 years
Net Regulatory Assets, Remaining Amortization Period, Max	44 years
Decoupling over-collection [Domain] | PUGET SOUND ENERGY, INC.
Regulation and Rates [Line Items]
Net Regulatory Assets, Remaining Amortization Period	1 year
Various other regulatory liabilities | PUGET SOUND ENERGY, INC.
Regulation and Rates [Line Items]
Net Regulatory Assets, Remaining Amortization Period, Max	4 years
Maximum | Property tax tracker | PUGET SOUND ENERGY, INC.
Regulation and Rates [Line Items]
Net Regulatory Assets, Remaining Amortization Period	2 years
Maximum | Decoupling Under-Collection | PUGET SOUND ENERGY, INC.
Regulation and Rates [Line Items]
Net Regulatory Assets, Remaining Amortization Period	2 years
Maximum | Deferred gain on Jefferson County sale | PUGET SOUND ENERGY, INC.
Regulation and Rates [Line Items]
Net Regulatory Assets, Remaining Amortization Period	1 year