Accounting for Derivative Instruments and Hedging Activities (Schedule of Contractual Contingent Liability Positions) (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012
Derivative [Line Items]
Fair Value Liability	$ (77,567)	[1]
Posted Collateral	0
Contingent Collateral	31,995
Forward Value of Contract
Derivative [Line Items]
Fair Value Liability	(4,261)	[1],[2]
Posted Collateral	0	[2]
Contingent Collateral	0	[2]
Requested Credit for Adequate Assurance
Derivative [Line Items]
Fair Value Liability	(41,311)	[1]
Posted Collateral	0
Contingent Collateral	0
Credit Rating
Derivative [Line Items]
Fair Value Liability	(31,995)	[1],[3]
Posted Collateral	0	[3]
Contingent Collateral	$ 31,995	[3]

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

[3] 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.