Fair Value Measurements (Tables)

6 Months Ended

Jun. 30, 2012

Fair Value Disclosures [Abstract]

Schedule of assets and liabilities measured at fair value on a recurring basis

The following table presents the Company's assets and liabilities that are measured at fair value as of June 30, 2012:

	Fair Value Measurement at the End of the Reporting Period Using
	Quoted Prices in Active Markets for Identical Assets (Level 1)		Significant Other Observable Inputs (Level 2)			Significant Unobservable Inputs (Level 3)		Fair Value at June 30, 2012
	(in thousands)
Recurring fair value measurements
Assets:
Trading securities	$	251	$	168		$	—	$	419
Commodity derivatives	—		569,691			—		569,691
Deferred compensation plan assets	44,191		—			—		44,191
Total assets	$	44,442	$	569,859		$	—	$	614,301
Liabilities:
Commodity derivatives	$	—	$	(13,742	)	$	—	$	(13,742	)
Interest rate derivatives	—		(34,693		)	—		(34,693		)
Total liabilities	$	—	$	(48,435	)	$	—	$	(48,435	)
Total recurring fair value measurements	$	44,442	$	521,424		$	—	$	565,866

Schedule of carrying values and financial instruments not carried at fair value

Carrying values and fair values of financial instruments that are not carried at fair value in the consolidated balance sheet as of June 30, 2012 and December 31, 2011 are as follows:

	June 30, 2012				December 31, 2011
	Carrying Value		Fair Value		Carrying Value		Fair Value
	(in thousands)
Long-term debt	$	3,285,497	$	3,934,014	$	2,528,905	$	3,105,585