Decommissioning Liabilities (Tables)

3 Months Ended

Mar. 31, 2012

Decommissioning Liabilities [Abstract]

Summary the activity for company's decommissioning liabilities

	2012			2011
Decommissioning liabilities, December 31, 2011 and 2010, respectively	$	123,176		$	117,716
Liabilities acquired and incurred		3,573			—
Liabilities settled		(2,661	)		—
Accretion		1,741			1,668
Total decommissioning liabilities, March 31, 2012 and 2011, respectively		125,829			119,384
Less: current portion of decommissioning liabilities at March 31, 2012 and 2011, respectively		15,678			17,063
Long-term decommissioning liabilities, March 31, 2012 and 2011, respectively	$	110,151		$	102,321