Accounting for Derivative Instruments and Hedging Activities (Schedule of Derivative Assets and Liabilities) (Details) (USD $)	Dec. 31, 2014		Dec. 31, 2013
Derivative [Line Items]
Assets, Current	$ 21,178,000		$ 18,867,000
Assets, Long-term	3,170,000		7,733,000
Liabilities, Current	142,195,000		48,049,000
Liabilities, Long-term	62,913,000		38,162,000
PUGET ENERGY
Derivative [Line Items]
Liabilities, Current	6,222,000		6,584,000
Liabilities, Long-term	2,850,000		6,656,000
PUGET SOUND ENERGY, INC.
Derivative [Line Items]
Assets, Current	21,178,000		18,867,000
Assets, Long-term	3,170,000		7,733,000
Liabilities, Current	135,973,000		41,465,000
Liabilities, Long-term	60,063,000		31,523,000
Interest Rate Swap | PUGET ENERGY
Derivative [Line Items]
Number of interest rate derivatives held	0
Commodity Contract
Derivative [Line Items]
Derivative Asset, Fair Value, Gross Asset	24,348,000	[1]	26,600,000	[1]
Total derivative assets	24,348,000		26,600,000
Total derivative liabilities	196,035,000		72,988,000
Derivative Asset, Collateral, Obligation to Return Cash, Offset	0		0
Derivative, Collateral, Obligation to Return Securities	(23,066,000)		(19,491,000)
Derivative, Collateral, Obligation to Return Cash	0		0
Derivative Asset, Fair Value, Amount Offset Against Collateral	1,282,000		7,109,000
Derivative Liability, Fair Value, Gross Liability	196,035,000	[1]	72,988,000	[1]
Derivative Liability, Collateral, Right to Reclaim Cash, Offset	0	[2]	0
Derivative, Collateral, Right to Reclaim Securities	(23,066,000)		(19,491,000)
Derivative, Collateral, Right to Reclaim Cash	(20,000)		0
Derivative Liability, Fair Value, Amount Offset Against Collateral	172,949,000		53,497,000
Natural Gas Portfolio
Derivative [Line Items]
Offsetting regulatory assets	69,300,000		27,600,000
Interest Rate Contract
Derivative [Line Items]
Total derivative liabilities	9,073,000	[2]	13,223,000	[2]
Derivative Liability, Fair Value, Gross Liability	9,073,000	[1],[2]	13,223,000	[1],[2]
Derivative Liability, Collateral, Right to Reclaim Cash, Offset			0	[2]
Derivative, Collateral, Right to Reclaim Securities	0	[2]	0	[2]
Derivative, Collateral, Right to Reclaim Cash	0	[2]	0	[2]
Derivative Liability, Fair Value, Amount Offset Against Collateral	9,073,000	[2]	13,223,000	[2]
Not Designated as Hedging Instrument
Derivative [Line Items]
Total derivative assets	24,348,000	[3]	26,600,000	[3]
Total derivative liabilities	205,108,000	[4]	86,211,000	[4]
Not Designated as Hedging Instrument | PUGET ENERGY
Derivative [Line Items]
Assets, Current	21,178,000	[3]	18,867,000	[3]
Assets, Long-term	3,170,000	[3]	7,733,000	[3]
Liabilities, Current	142,195,000	[4]	48,049,000	[4]
Liabilities, Long-term	62,913,000	[4]	38,162,000	[4]
Not Designated as Hedging Instrument | Interest Rate Swap
Derivative [Line Items]
Derivative, Notional Amount	450,000,000	[5]	450,000,000	[5]
Total derivative assets	0	[3],[5]	0	[3],[5]
Total derivative liabilities	9,073,000	[4],[5]	13,223,000	[4],[5]
Not Designated as Hedging Instrument | Electric Generation Fuel
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount	140,200,000		145,600,000
Not Designated as Hedging Instrument | Purchased Electricity
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount	5,400,000		8,600,000
Not Designated as Hedging Instrument | Electric Portfolio
Derivative [Line Items]
Total derivative assets	4,822,000	[3]	18,479,000	[3]
Total derivative liabilities	107,228,000	[4]	37,312,000	[4]
Not Designated as Hedging Instrument | Natural Gas Portfolio
Derivative [Line Items]
Total derivative assets	19,526,000	[3],[6]	8,121,000	[3],[6]
Total derivative liabilities	$ 88,807,000	[4],[6]	$ 35,676,000	[4],[6]
Not Designated as Hedging Instrument | Gas Derivatives
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount	360,400,000	[6]	423,500,000	[6]

[1] All Derivative Contract deals are executed under ISDA, NAESB and WSPP Master Netting Agreements with Right of Offset.

[2] Interest Rate Swap Contracts are only held at Puget Energy.

[3] Balance sheet location: Current and Long-term Unrealized gain on derivative instruments.

[4] Balance sheet location: Current and Long-term Unrealized loss on derivative instruments.

[5] Interest rate swap contracts are only held at Puget Energy.

[6] PSE had a net derivative liability and an offsetting regulatory asset of $69.3 million at December 31, 2014 and $27.6 million at December 31, 2013 related to contracts used to economically hedge the cost of physical gas purchased to serve natural gas customers. All fair value adjustments on derivatives relating to the natural gas business have been deferred in accordance with ASC 980, due to the PGA mechanism.