Fair Value Measurements (Tables)

6 Months Ended

Jun. 30, 2012

Fair Value Measurements [Abstract]

Assets and liabilities measured at Fair Value on Recurring basis

	Level 1		Level 2			Level 3		Total Net Fair Value
At December 31, 2011
Equity investment	$	11,601	$	1,393		$	—	$	12,994
Derivative financial instruments — assets		—		72,319			—		72,319
Derivative financial instruments — liabilities		—		(9,834	)		—		(9,834	)
Total	$	11,601	$	63,878		$	—	$	75,479
At June 30, 2012
Equity investment	$	9,352	$	1,119		$	—	$	10,471
Derivative financial instruments — assets		—		51,594			—		51,594
Derivative financial instruments — liabilities		—		(8,423	)		—		(8,423	)
Total	$	9,352	$	44,290		$	—	$	53,642

Reconciliation of changes in Fair Value of risk management assets and liabilities

	Six Months Ended June  30, 2011
Balance at beginning of period	$	(9,853	)
Realized and unrealized gains included in earnings		(2,025	)
Transfers out of Level 3 (1)		9,949
Settlements		1,929
Balance at end of period	$	—

(1) Availability of market based information allowed the Company to reclassify all if its swap contracts tied to Southern Star prices from Level 3 to Level 2 during the second quarter of 2011.