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Supplemental Oil and Gas Disclosures (Unaudited) - 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
Extractive Industries [Abstract]      
Standardized measure, beginning of year $ 2,537,595 $ 3,340,246 $ 1,807,669
Sales and transfers of oil, net gas and NGLs produced during the period (339,557) (665,226) (727,969)
Net change in prices and production costs (1,468,304) (849,696) 1,578,330
Changes in estimated future development costs 32,589 (75,564) 32,328
Previously estimated development costs incurred 46,143 117,049 45,937
Accretion of discount 299,302 392,526 180,767
Net change in income taxes 361,875 129,590 (585,017)
Purchases of reserves 730,611 75,009 943,519
Extensions and discoveries 71,589 306,515 148,068
Net change due to revision in quantity estimates (309,338) (199,576) 190,853
Changes in production rates (timing) and other (57,571) (33,278) (274,239)
Standardized measure, end of year $ 1,904,934 $ 2,537,595 $ 3,340,246