Asset Retirement Obligations

6 Months Ended

Jun. 30, 2013

Asset Retirement Obligation Disclosure [Abstract]

Asset Retirement Obligations

The following table summarizes the activity for the Company's asset retirement obligations (AROs) for the six months ended June 30, 2013 and 2012:



	Six Months Ended
	June 30,
(in thousands)	2013			2012
Beginning balance at January 1	$	86,746		$	64,019
Liabilities incurred	4,700			4,024
Liabilities settled	(2,007		)	(1,668		)
Liabilities assumed	—			1,626
Disposition of assets	(40		)	(705		)
Accretion expense	3,548			2,596
Revisions in estimated cash flows	5,907			10,988
Ending balance at June 30	$	98,854		$	80,880

ARO reflects the estimated present value of the amount of dismantlement, removal, site reclamation and similar activities associated with the Company's oil and natural gas properties. Inherent in the fair value calculation of ARO are numerous assumptions and judgments including the ultimate settlement amounts, inflation factors, credit adjusted discount rates, timing of settlement and changes in the legal, regulatory, environmental and political environments. To the extent future revisions to these assumptions impact the fair value of the existing ARO liability, a corresponding adjustment is made to the oil and natural gas property balance.