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Dispositions - Additional Information (Detail)
 1 Months Ended 3 Months Ended 12 Months Ended
Aug. 14, 2020
USD ($)
Aug. 31, 2020
USD ($)
Sep. 30, 2020
USD ($)
Mar. 31, 2020
USD ($)
Sep. 30, 2019
USD ($)
Jun. 30, 2019
USD ($)
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Dec. 31, 2018
USD ($)
Sep. 30, 2018
USD ($)
Dec. 31, 2020
USD ($)
Dec. 31, 2019
USD ($)
Dec. 31, 2018
USD ($)
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]                      
(Loss) gain on the sale of assets                 $ 110,791,000 $ (30,256,000) $ (10,666,000)
Proceeds from disposal of assets                 246,127,000 784,937,000 324,549,000
Estimated fair value of contingent consideration                 74,602,000 152,692,000  
Miscellaneous Proved, Unproved Properties and Surface Acreage                      
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]                      
(Loss) gain on the sale of assets                 2,200,000 337,000 (448,000)
Proceeds from sale of oil and gas properties                 127,000 $ 938,000 $ 1,200,000
Northern Oklahoma                      
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]                      
(Loss) gain on the sale of assets               $ (39,000)      
Proceeds from sale of oil and gas properties               $ 23,300,000      
Contingent Consideration                      
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]                      
Estimated fair value of contingent consideration                 15,960,000    
North Louisiana                      
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]                      
(Loss) gain on the sale of assets                 (9,500,000)    
Fair value of total consideration for sale $ 260,000,000.0                    
Proceeds from disposal of assets 245,000,000.0                    
Divestiture fee obligation 479,800,000                    
Unrealized loss for novated derivatives 12,100,000                    
North Louisiana | Contingent Consideration                      
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]                      
Estimated fair value of contingent consideration $ 15,000,000.0                    
North Louisiana | Contingent Consideration | Maximum                      
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]                      
Potential Contractual Payout Of Contingent Consideration   $ 90,000,000 $ 90,000,000.0           $ 90,000,000.0    
Northwest Pennsylvania                      
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]                      
(Loss) gain on the sale of assets       $ 122,500,000              
Proceeds from sale of oil and gas properties       $ 1,000,000.0              
Pennsylvania                      
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]                      
(Loss) gain on the sale of assets         $ (36,500,000) $ 5,900,000 $ (10,200,000)        
Proceeds from sale of oil and gas properties         $ 750,000,000.0 $ 34,000,000.0 $ 300,000,000.0        
Percentage of royalty disposed         2.50%   1.00%       1.00%
Pennsylvania | Natural Gas and Oil Properties                      
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]                      
Number of acres sold | a           20,000