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Supplemental Information on Natural Gas and Oil Exploration, Development and Production Activities (Unaudited) - Costs Incurred for Property Acquisition, Exploration and Development (Detail) - USD ($)
$ in Thousands
12 Months Ended
Dec. 31, 2018
Dec. 31, 2017
Dec. 31, 2016
Acquisitions      
Acreage purchases [1] $ 62,390 $ 62,075 $ 33,142
Oil and gas properties [1] 1,683 18,269 3,098,772
Asset retirement obligations and other [1]     21,908
Development [1] 834,552 1,177,526 497,795
Exploration:      
Exploration drilling costs incurred [1] 1,380 2,030 37,680
Gas gathering facilities:      
Development [1] 10,218 15,097 3,595
Subtotal [1] 944,340 1,328,659 3,725,217
Asset retirement obligations [1] 28,826 20,245 (24,064)
Total costs incurred [1] 973,166 1,348,904 3,701,153
Expense      
Exploration:      
Exploration costs incurred [1] 32,196 50,920 30,027
Stock-based compensation expense [1] $ 1,921 $ 2,742 $ 2,298
[1] Includes cost incurred whether capitalized or expensed.