Schedule of Principal Changes in Standardized Measure of Discounted Future Net Cash Flows (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Increase (Decrease) in Standardized Measure of Discounted Future Net Cash Flows Relating to Proved Oil and Gas Reserves [Roll Forward]
Standardized measure of discounted future net cash flows at the beginning of the period	$ 458,350	$ 608,870	$ 595,579
Purchase of minerals in place	2,134	1,256	1,092
Sales of oil and natural gas, net of production costs	(35,281)	(59,949)	(91,180)
Extensions and discoveries	1,462	9,711
Net changes in prices and production costs	(148,892)	(91,386)	165,659
Revisions of previous quantity estimates	(72,896)	(92,479)	41,728
Divestiture of reserves			(73,755)
Net changes in income taxes	25,419	20,613	(49,758)
Accretion of discount	44,279	65,863	59,558
Net changes in timing of production and other	(22,763)	(4,149)	(40,053)
Standardized measure of discounted future net cash flows at the end of the period	$ 251,812	$ 458,350	$ 608,870