Fair Value Measurements (Tables)

12 Months Ended

Dec. 31, 2012

Fair Value Disclosures [Abstract]

Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis

December 31, 2012	Quoted Prices in Active Markets for Identical Assets or Liabilities (Level 1)		Significant Other Observable Inputs (Level 2)			Significant Unobservable Inputs (Level 3)		Margin Cash Collateral Offset		Total Net Fair Value
	(in thousands)
Restricted cash	$	6,392	$	—		$	—	$	—	$	6,392
Rabbi trust investments	10,522		—			—		—		10,522
Derivative liability (1)	—		(5,428		)	—		—		(5,428		)
Total	$	16,914	$	(5,428	)	$	—	$	—	$	11,486
December 31, 2011
Restricted cash	$	12,292	$	—		$	—	$	—	$	12,292
Rabbi trust investments	8,049		—			—		—		8,049
Derivative liability (1)	—		(20,312		)	—		—		(20,312		)
Total	$	20,341	$	(20,312	)	$	—	$	—	$	29

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(1) The changes in the fair value of these derivatives are deferred as a regulatory asset or liability until the contracts are settled. Upon settlement, associated proceeds or costs are passed through the applicable cost tracking mechanism to customers.

Schedule of Estimated Fair Value of Financial Instruments

The estimated fair value of financial instruments is summarized as follows (in thousands):

	December 31, 2012				December 31, 2011
	Carrying Amount		Fair Value		Carrying Amount		Fair Value
Liabilities:
Long-term debt (including current portion)	$	1,055,074	$	1,229,233	$	908,841	$	1,070,539