Accounting for Derivative Instruments and Hedging Activities Derivative Activity and Notional Amounts (Details) MWh in Millions, MMBTU in Millions, $ in Millions		Jun. 30, 2015 USD ($) MWh MMBTU Contracts	Dec. 31, 2014 USD ($) MWh MMBTU
Interest Rate Swap [Member] | Not Designated as Hedging Instrument [Member]
Derivative [Line Items]
Derivative, Notional Amount | $	[1]	$ 450	$ 450
Natural Gas Derivatives [Member] | Not Designated as Hedging Instrument [Member]
Derivative [Line Items]
Derivative, Notional amount, Nonmonetary	[2]	343.0	360.4
Electric generation fuel [Member] | Not Designated as Hedging Instrument [Member]
Derivative [Line Items]
Derivative, Notional amount, Nonmonetary		171.6	140.2
Purchased Electricity [Member] | Not Designated as Hedging Instrument [Member]
Derivative [Line Items]
Derivative, Notional amount, Nonmonetary | MWh		4.1	5.4
Parent Company [Member] | Interest Rate Swap [Member]
Derivative [Line Items]
Number of Interest Rate Derivatives Held | Contracts		2

[1] 3 Interest rate swap contracts are only held at Puget Energy.

[2] 4 All fair value adjustments on derivatives relating to the natural gas business have been deferred in accordance with Accounting Standards Codification (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.