Asset Retirement Obligations (Tables)

9 Months Ended

Sep. 30, 2014

Asset Retirement Obligation [Abstract]

Asset Retirement Obligations

The following table describes the changes to the Company’s asset retirement obligation liability for the following periods:

	Nine Months Ended
	September 30,
	2014			2013
	(in thousands)
Asset retirement obligation, beginning of period	$	3,029		$	2,145
Additional liability incurred	567			162
Liabilities acquired	3,678			471
Liabilities settled	(10		)	(14		)
Accretion expense	303			134
Revisions in estimated liabilities	588			—
Asset retirement obligation, end of period	8,155			2,898
Less current portion	40			20
Asset retirement obligations - long-term	$	8,115		$	2,878