Organization and Significant Accounting Policies (Tables)

12 Months Ended

Dec. 31, 2017

Organization, Consolidation and Presentation of Financial Statements [Abstract]

Asset Retirement Obligations

The following table summarizes the Company’s future site restoration obligations during the two years ended December 31: 

		2016			2017
	(in thousands)
Beginning asset retirement obligation		$	9,679		$	8,623
New wells placed on production and other		119			1,088
Property acquisitions and dispositions, net		(1,832		)	(1,551		)
Accretion expense		491			451
Revisions		166			164
Ending asset retirement obligation		$	8,623		$	8,775