Annual report pursuant to Section 13 and 15(d)

Supplemental Information on Oil and Gas Producing Activities (Unaudited) - Changes in standardized measure of discounted future net cash flow (Detail)

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Supplemental Information on Oil and Gas Producing Activities (Unaudited) - Changes in standardized measure of discounted future net cash flow (Detail)
$ in Thousands
12 Months Ended
Dec. 31, 2019
USD ($)
$ / MMcfe
Dec. 31, 2018
USD ($)
$ / MMcfe
Dec. 31, 2017
USD ($)
$ / MMcfe
Supplemental Information on Oil and Gas Producing Activities (Unaudited)      
Weighted average price of equivalent reserves (in dollar per share) | $ / MMcfe 2.87 3.56 3.23
Changes in Standardized Measure of Discounted Future Net Cash Flow      
Sales of oil and gas, net of productions costs $ (1,116) $ (2,051) $ (1,469)
Net changes in prices and production costs (6,729) 707 3,918
Development costs incurred during the period 758 755 627
Net changes in future development costs (92) 37 229
Extensions, discoveries and other additions 782 1,925 1,448
Acquisitions     258
Revisions of previous quantity estimates (1,011) (53) 734
Accretion of discount 1,259 1,018 368
Net change in income taxes 1,513 (563) (1,159)
Changes in timing and other (373) 76 386
Net increase (decrease) (5,009) 1,851 5,340
Beginning of year 10,478 8,627 3,287
End of year 5,469 $ 10,478 $ 8,627
Increased production costs 3,300,000    
Increased future development costs $ 185,000