Accounting for Derivative Instruments and Hedging Activities Contractual Contingent Liability (Details) (Electric portfolio [Member], USD $) In Thousands, unless otherwise specified	Jun. 30, 2012
Derivative [Line Items]
Fair Value Liability	$ (124,862)	[1]
Posted Collateral	0
Contingent Collateral	37,833
Credit rating [Member]
Derivative [Line Items]
Fair Value Liability	(37,833)	[1],[2]
Posted Collateral	0	[2]
Contingent Collateral	37,833	[2]
Requested credit for adequate assurance [Member]
Derivative [Line Items]
Fair Value Liability	(74,936)	[1]
Posted Collateral	0
Contingent Collateral	0
Forward value of contract [Member]
Derivative [Line Items]
Fair Value Liability	(12,093)	[1],[3]
Posted Collateral	0	[3]
Contingent Collateral	$ 0	[3]
External Credit Rating, Investment Grade [Member]
Derivative [Line Items]
Derivative, Credit Risk Exposure, Percentage	99.90%
External Credit Rating, Non Investment Grade [Member]
Derivative [Line Items]
Derivative, Credit Risk Exposure, Percentage	0.10%

[1] Represents the derivative fair value of contracts with contingent features for counterparties in net derivative liability positions at June 30, 2012. Excludes NPNS, accounts payable and accounts receivable.

[2] Failure by PSE to maintain an investment grade credit rating from each of the major credit rating agencies provides counterparties a contractual right to demand collateral.

[3] Collateral requirements may vary, based on changes in the forward value of underlying transactions relative to contractually defined collateral thresholds.