Derivative Financial Instruments (Tables)

12 Months Ended

Dec. 31, 2011

Derivative Instruments and Hedging Activities Disclosure [Abstract]

Schedule of fair value of derivatives in accompanying balance sheets

The following table details the fair value of derivatives recorded in the accompanying balance sheets, by category:

	As of December 31, 2011
	Derivative Assets			Derivative Liabilities
	Balance Sheet  Classification	Fair Value		Balance Sheet  Classification	Fair Value
	(in thousands)
Commodity Contracts	Current Assets	$	55,813	Current Liabilities	$	42,806
Commodity Contracts	Noncurrent Assets	31,062		Noncurrent liabilities	12,875
Derivatives not designated as hedging instruments		$	86,875		$	55,681

	As of December 31, 2010
	Derivative Assets			Derivative Liabilities
	Balance Sheet  Classification	Fair Value		Balance Sheet  Classification	Fair Value
	(in thousands)
Commodity Contracts	Current Assets	$	43,491	Current Liabilities	$	82,044
Commodity Contracts	Noncurrent Assets	18,841		Noncurrent Liabilities	32,557
Derivatives designated as hedging instruments		$	62,332		$	114,601

Schedule of unrealized and realized gains and losses on derivative instruments in the statement of operations

The following table summarizes the unrealized and realized gains and losses on derivative cash settlements and changes in fair value of derivative contracts not designated as hedging instruments as presented in the accompanying statements of operations.

	For the year ended December 31, 2011
	(in thousands)
Cash settlement (gain) loss:
Oil contracts	$	22,633
Natural gas contracts	(10,711		)
NGL contracts	13,749
Total cash settlement loss	$	25,671
Unrealized (gain) loss on changes in fair value:
Oil contracts	$	(3,391	)
Natural gas contracts	(64,310		)
NGL contracts	4,944
Total net unrealized (gain) on change in fair value	$	(62,757	)
Total unrealized and realized derivative (gain) loss	$	(37,086	)

Detail of the effect of derivative instruments reclassified from AOCI to the statement of operations (net of income tax)

The following table details the effect of derivative instruments on AOCIL and the accompanying statements of operations (net of income tax):

		Location on Accompanying Statements of Operations	For the Years Ended December 31,
	Derivatives		2011		2010		2009
			(in thousands)
Amount reclassified from AOCIL to realized hedge (loss) gain	Commodity Contracts	Realized hedge (loss) gain	$	12,997	$	6,641	$	(67,344	)

Detail of the effect of derivative instruments on AOCIL and the accompanying balance sheets (net of income taxes)

The following table details the effect of derivative instruments on AOCIL and the accompanying balance sheets (net of income tax):

	Derivatives	Location on Accompanying Balance Sheets	For the years ended December 31,
			2010		2009
			(in thousands)
Amount of gain (loss) on derivatives recognized in AOCIL during the period (effective portion)	Commodity Contracts	AOCIL	$	16,811	$	(35,977	)

Detail of the effect of derivative instruments on other comprehensive income (loss) and the accompanying statements of operations (net of income taxes)

The following table details the ineffective portion of derivative instruments classified as cash flow hedges on the accompanying statements of operations for the years ended December 31, 2010 and 2009.

		Loss Recognized in Earnings (Ineffective Portion)
	Location on Accompanying  Statements of  Operations
Derivatives Qualifying as Cash Flow Hedges
		For the Years Ended December 31,
		2010		2009
		(in thousands)
Commodity Contracts	Unrealized and realized derivative (gain) loss	$	8,899	$	20,469