Annual report pursuant to Section 13 and 15(d)

Supplemental Information on Oil and Natural Gas Properties (Unaudited) (Standardized Measure of Discounted Future Cash Flows Relating to Proved Reserves Disclosure) (Details)

v3.20.4
Supplemental Information on Oil and Natural Gas Properties (Unaudited) (Standardized Measure of Discounted Future Cash Flows Relating to Proved Reserves Disclosure) (Details) - USD ($)
$ in Thousands
12 Months Ended
Dec. 31, 2020
Dec. 31, 2019
Dec. 31, 2018
Dec. 31, 2020
Dec. 31, 2019
Dec. 31, 2018
Future Net Cash Flows Relating to Proved Oil and Gas Reserves, Net Cash Flows [Abstract]            
Future cash inflows       $ 12,458,033 $ 20,891,469 $ 11,794,080
Future costs            
Production       (5,433,496) (6,717,088) (2,923,959)
Development and net abandonment       (2,204,301) (3,058,861) (1,429,787)
Future net inflows before income taxes       4,820,236 11,115,520 7,440,334
Future income taxes       (65,405) (941,768) (782,470)
Future net cash flows       4,754,831 10,173,752 6,657,864
10% discount factor       (2,444,441) (5,222,726) (3,716,571)
Standardized measure of discounted future net cash flows $ 4,951,026 $ 2,941,293 $ 2,941,293 $ 2,310,390 $ 4,951,026 $ 2,941,293
Increase (Decrease) in Standardized Measure of Discounted Future Net Cash Flows Relating to Proved Oil and Gas Reserves [Roll Forward]            
Standardized measure at the beginning of the period 4,951,026 2,941,293 1,556,682      
Sales and transfers, net of production costs (649,781) (579,744) (481,306)      
Net change in sales and transfer prices, net of production costs (2,719,579) (387,970) 222,802      
Net change due to purchases of in place reserves 0 2,975,296 554,697      
Net change due to sales of in place reserves (202,928) (303,526) 0      
Extensions, discoveries, and improved recovery, net of future production and development costs incurred 250,759 607,146 1,001,873      
Changes in future development cost 361,008 205,398 40,483      
Previously estimated development costs incurred 318,470 134,037 91,900      
Revisions of quantity estimates (671,800) (420,488) (167,096)      
Accretion of discount 536,958 314,921 157,676      
Net change in income taxes 383,999 (210,641) (187,841)      
Changes in production rates, timing and other (247,742) (324,696) 151,423      
Aggregate change (2,640,636) 2,009,733 1,384,611      
Standardized measure at the end of period $ 2,310,390 $ 4,951,026 $ 2,941,293