Supplemental Balance Sheet (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Prepaid and other current assets:
Inventories 1	$ 4,036	$ 4,274
Prepaid expenses 2	15,511	14,771
Other Assets, Current	19,547	19,045
Other assets:
Deferred issuance costs of the Revolver	2,542	2,349
Operating Lease, Right-of-Use Asset	2,237	2,432
Other	127	127
Other assets	4,906	4,908
Accounts payable and accrued liabilities:
Trade accounts payable	29,137	7,055
Drilling and other lease operating costs	18,002	16,088
Royalties	34,223	26,615
Production, ad valorem and other taxes	5,242	3,094
Derivative Liability Settlements to Counterparties	8,773	321
Compensation	2,270	4,222
Interest	401	504
Operating Lease, Liability, Current	894	936
Other	1,008	4,254
Accounts payable and accrued liabilities	99,950	63,089
Other liabilities:
Asset retirement obligations	5,648	5,461
Noncurrent operating lease obligations	1,553	1,752
Defined benefit pension obligations	845	865
Postretirement health care benefit obligations	291	284
Other Liabilities, Noncurrent	8,337	8,362
Tubular Inventory and Well Materials	3,300	3,900
Capitalized Costs - Crude Oil in Storage	700	400
Drilling and Completion Prepayment	$ 13,900	13,600
Accrued Expenses - Juniper Transaction		$ 3,500