Accounting for Derivative Instruments and Hedging Activities Derivative Assets and Liabilities (Details) (USD $)	6 Months Ended
	Jun. 30, 2013		Dec. 31, 2012
Derivative [Line Items]
Document Period End Date	Jun. 30, 2013
Unrealized gain on derivative instruments	$ 10,026,000		$ 6,869,000
Assets, Long-term	6,865,000		14,814,000
Unrealized loss on derivative instruments	115,038,000		177,519,000
Unrealized loss on derivative instruments	59,392,000		83,276,000
Subsidiaries [Member]
Derivative [Line Items]
Document Period End Date	Jun. 30, 2013
Unrealized gain on derivative instruments	10,026,000		6,869,000
Assets, Long-term	6,865,000		14,814,000
Unrealized loss on derivative instruments	108,520,000		170,948,000
Unrealized loss on derivative instruments	52,205,000		68,323,000
Offsetting regulatory assets	70,400,000		96,000,000
Commodity Contract [Member]
Derivative [Line Items]
Assets	16,891,000		21,683,000
Liabilities	160,725,000		239,271,000
Not Designated as Hedging Instrument [Member]
Derivative [Line Items]
Assets	16,891,000	[1]	21,683,000	[1]
Liabilities	174,430,000	[2]	260,795,000	[2]
Not Designated as Hedging Instrument [Member] | PUGET ENERGY [Member]
Derivative [Line Items]
Unrealized gain on derivative instruments	10,026,000	[1]	6,869,000	[1]
Assets, Long-term	6,865,000	[1]	14,814,000	[1]
Unrealized loss on derivative instruments	115,038,000	[2]	177,519,000	[2]
Unrealized loss on derivative instruments	59,392,000	[2]	83,276,000	[2]
Not Designated as Hedging Instrument [Member] | Interest rate swaps [Member]
Derivative [Line Items]
Derivative, Notional Amount	450,000,000	[3]	450,000,000	[3]
Assets	0	[1],[3]	0	[1],[3]
Liabilities	13,706,000	[2],[3]	21,524,000	[2],[3]
Not Designated as Hedging Instrument [Member] | Electric portfolio [Member]
Derivative [Line Items]
Assets	10,474,000	[1]	9,557,000	[1]
Liabilities	83,957,000	[2]	131,193,000	[2]
Not Designated as Hedging Instrument [Member] | Natural gas portfolio [Member]
Derivative [Line Items]
Assets	6,417,000	[1],[4]	12,126,000	[1],[4]
Liabilities	$ 76,767,000	[2],[4]	$ 108,078,000	[2],[4]
Not Designated as Hedging Instrument [Member] | Natural Gas Derivatives [Member]
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount	459,420,774	[4]	516,909,006	[4]

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

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

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

[4] PSE had a net derivative liability and an offsetting regulatory asset of $70.4 million at June 30, 2013 and $96.0 million at December 31, 2012 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 reclassified to a deferred account in accordance with ASC 980, “Regulated Operations” (ASC 980) due to the Purchased Gas Adjustment (PGA) mechanism.