Accounting for Derivative Instruments and Hedging Activities Derivative Assets and Liabilities (Details) (USD $)	Sep. 30, 2014		Dec. 31, 2013
Derivative [Line Items]
Unrealized gain on derivative instruments	$ 14,832,000		$ 18,867,000
Assets, Long-term	4,718,000		7,733,000
Unrealized loss on derivative instruments	37,410,000		48,049,000
Unrealized loss on derivative instruments	24,457,000		38,162,000
Subsidiaries [Member]
Derivative [Line Items]
Unrealized gain on derivative instruments	14,832,000		18,867,000
Assets, Long-term	4,718,000		7,733,000
Unrealized loss on derivative instruments	30,868,000		41,465,000
Unrealized loss on derivative instruments	21,439,000		31,523,000
Commodity Contract [Member]
Derivative [Line Items]
Assets	19,550,000		26,600,000
Derivative Liability	52,307,000		72,988,000
Not Designated as Hedging Instrument [Member]
Derivative [Line Items]
Assets	19,550,000	[1]	26,600,000	[1]
Derivative Liability	61,867,000	[2]	86,211,000	[2]
Not Designated as Hedging Instrument [Member] | Parent Company [Member]
Derivative [Line Items]
Unrealized gain on derivative instruments	14,832,000	[1]	18,867,000	[1]
Assets, Long-term	4,718,000	[1]	7,733,000	[1]
Unrealized loss on derivative instruments	37,410,000	[2]	48,049,000	[2]
Unrealized loss on derivative instruments	24,457,000	[2]	38,162,000	[2]
Not Designated as Hedging Instrument [Member] | Interest Rate Swap [Member]
Derivative [Line Items]
Derivative, Notional Amount	450,000,000	[3]	450,000,000	[3]
Assets	0	[1],[3]	0	[1],[3]
Derivative Liability	9,560,000	[2],[3]	13,223,000	[2],[3]
Not Designated as Hedging Instrument [Member] | Electric portfolio [Member]
Derivative [Line Items]
Assets	7,160,000	[1]	18,479,000	[1]
Derivative Liability	33,172,000	[2]	37,312,000	[2]
Not Designated as Hedging Instrument [Member] | Natural gas portfolio [Member]
Derivative [Line Items]
Assets	12,390,000	[1],[4]	8,121,000	[1],[4]
Derivative Liability	$ 19,135,000	[2],[4]	$ 35,676,000	[2],[4]
Not Designated as Hedging Instrument [Member] | Natural Gas Derivatives [Member]
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount	394,300,000	[4]	423,500,000	[4]

[1] 1 Balance sheet location: Current and Long-term Unrealized gain on derivative instruments.

[2] 2 Balance sheet location: Current and Long-term Unrealized loss on derivative instruments.

[3] 3 Interest rate swap contracts are only held at Puget Energy.

[4] 4 All fair value adjustments on derivatives relating to the natural gas business have been deferred in accordance with ASC 980, “Regulated Operations” (ASC 980) due to the PGA mechanism. The net derivative asset or liability and offsetting regulatory liability or asset are related to contracts used to economically hedge the cost of physical gas purchased to serve natural gas customers.