Schedule of Standardized Measure of Discounted Future Net Cash Flows Relating to Proved Oil and Natural Gas Reserves (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Extractive Industries [Abstract]
Future cash inflows	$ 476,315	$ 882,076	$ 1,265,153
Future production costs	(41,770)	(70,956)	(98,672)
Future income tax expense	(6,431)	(48,040)	(87,803)
Future net cash flows	428,114	763,080	1,078,678
10% discount to reflect timing of cash flows	(176,302)	(304,730)	(469,808)
Standardized measure of discounted cash flows	$ 251,812	$ 458,350	$ 608,870	$ 595,579