Supplemental Balance Sheet (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019	Jun. 30, 2019
Other current assets:
Tubular inventory and well materials	$ 2,995	$ 2,989
Prepaid expenses	1,146	1,469
Other Assets, Current	4,141	4,458
Other assets:
Deferred issuance costs of the Revolver	2,693	3,952
Operating Lease, Right-of-Use Asset	2,734	2,740
Other	110	32
Other assets	5,537	6,724
Accounts payable and accrued liabilities:
Trade accounts payable	10,706	30,098
Drilling costs	10,888	18,832
Royalties	23,045	44,537
Production, ad valorem and other taxes	4,874	3,244
Compensation	3,309	5,272
Interest	591	730
Operating Lease, Liability, Current	886	847	$ 886
Other	1,625	2,264
Accounts payable and accrued liabilities	55,924	105,824
Other liabilities:
Asset retirement obligations	5,183	4,934
Noncurrent operating lease obligations	2,142	2,232
Defined benefit pension obligations	814	873
Postretirement health care benefit obligations	371	343
Other	1,068	0
Other liabilities	$ 9,578	$ 8,382