Components of Selected Balance Sheet Accounts (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018
Other current assets:
Tubular inventory and well materials	$ 3,733		$ 4,061
Prepaid expenses	1,000		1,064
Other Assets, Current	4,733		5,125
Other assets:
Deferred issuance costs of the Revolver	4,308		2,437
Operating Lease, Right-of-Use Asset	3,059	$ 2,500	0
Other	45		44
Other assets	7,412		2,481
Accounts payable and accrued liabilities:
Trade accounts payable	15,712		16,507
Drilling costs	39,831		22,434
Royalties and revenue – related	43,903		51,212
Production, ad valorem and other taxes	5,236		2,418
Compensation – related	3,295		4,489
Interest	673		670
Operating Lease, Liability, Current	874		0
Other	2,469		5,970
Accounts payable and accrued liabilities	111,993		103,700
Other liabilities:
Asset retirement obligations	4,497		4,314
Operating Lease, Liability, Noncurrent	2,545		0
Defined benefit pension obligations	802		857
Postretirement health care benefit obligations	392		362
Other liabilities	$ 8,236		$ 5,533