Asset Retirement Obligations

3 Months Ended

Mar. 31, 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 three months ended March 31, 2013 and 2012:



	Three Months Ended
	March 31,
(in thousands)	2013			2012
Beginning balance at January 1	$	86,746		$	64,019
Liabilities incurred	2,711			2,993
Liabilities settled	(805		)	(467		)
Disposition of assets	—			(705		)
Accretion expense	1,704			1,223
Revisions in estimated cash flows	4,311			2,001
Ending balance at March 31	$	94,667		$	69,064

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.

- Definition

The entire disclosure for an asset retirement obligation and the associated long-lived asset. An asset retirement obligation is a legal obligation associated with the disposal or retirement from service of a tangible long-lived asset that results from the acquisition, construction or development, or the normal operations of a long-lived asset, except for certain obligations of lessees.

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