Accounting for Derivative Instruments and Hedging Activities Contractual Contingent Liability (Details) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2013
Electric portfolio [Member]
Derivative [Line Items]
Fair Value Liability	$ (69,124)	[1]
Posted Collateral	0
Additional Collateral, Aggregate Fair Value	37,598
Electric portfolio [Member] | Credit rating [Member]
Derivative [Line Items]
Fair Value Liability	(37,598)	[1],[2]
Posted Collateral	0	[2]
Additional Collateral, Aggregate Fair Value	37,598	[2]
Electric portfolio [Member] | Requested credit for adequate assurance [Member]
Derivative [Line Items]
Fair Value Liability	(31,358)	[1]
Posted Collateral	0
Additional Collateral, Aggregate Fair Value	0
Electric portfolio [Member] | Forward value of contract [Member]
Derivative [Line Items]
Fair Value Liability	(168)	[1],[3]
Posted Collateral	0	[3]
Additional Collateral, Aggregate Fair Value	0	[3]
Electric portfolio [Member] | External Credit Rating, Investment Grade [Member]
Derivative [Line Items]
Derivative, Credit Risk Exposure, Percentage	99.90%
Electric portfolio [Member] | External Credit Rating, Non Investment Grade [Member]
Derivative [Line Items]
Derivative, Credit Risk Exposure, Percentage	0.10%
Natural gas portfolio [Member] | Credit rating [Member]
Derivative [Line Items]
Posted Collateral	$ 0	[2]

[1] Represents the derivative fair value of contracts with contingent features for counterparties in net derivative liability positions. 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.