Asset Retirement Obligations (Tables)

12 Months Ended

Dec. 31, 2017

Asset Retirement Obligation Disclosure [Abstract]

Asset Retirement Obligation

The following is a reconciliation of our liability for plugging and abandonment costs as of December 31, 2017 and 2016 (in thousands):

	2017			2016
Beginning of period	$	257,943		$	264,137
Liabilities incurred		7,724			2,694
Acquisitions		—			21,900
Liabilities settled		(7,965	)		(11,511	)
Disposition of wells		(8,078	)		(10,540	)
Accretion expense		14,711			18,021
Change in estimate		12,520			(26,758	)
End of period		276,855			257,943
Less current portion		(6,327	)		(7,271	)
Long-term asset retirement obligations	$	270,528		$	250,672