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Summary of Significant Accounting Policies - Additional Information (Detail)
$ / shares in Units, $ in Thousands
12 Months Ended
Dec. 31, 2018
USD ($)
Customer
Segment
Dec. 31, 2017
USD ($)
Customer
Dec. 31, 2016
USD ($)
Customer
$ / shares
Summary Of Significant Accounting Policies [Line Items]      
Accounts receivable $ 119,332 $ 77,609 $ 44,423
Capitalized interest expense 1,700 2,300 1,100
Depreciation, depletion and amortization $ 134,277 $ 118,818 92,948
Impairment of oil and gas properties     17,665
Asset retirement obligations credit adjusted discount rates 10.33% 10.33%  
Operating lease expiration year 2024    
Number of operating segment | Segment 1    
Decrease in accounts receivable $ 42,879 $ 31,780 $ 21,277
Increase of net loss, per common share | $ / shares     $ (12.84)
Decrease in accrual for production and ad valorem taxes to be paid     $ 4,000
Decrease of net loss, per common share | $ / shares     $ 0.30
Natural Gas and NGLs [Member]      
Summary Of Significant Accounting Policies [Line Items]      
Decrease in accounts receivable     $ (4,000)
Increase in revenue from oil and natural gas     1,500
Increase in transportation, gathering and compression expense     5,800
Increase in net loss     $ 4,000
Increase of net loss, per common share | $ / shares     $ 0.02
Topic 842 [Member]      
Summary Of Significant Accounting Policies [Line Items]      
Operating lease ROU asset 10,000    
Operating lease liability 15,000    
Oil and Gas Properties [Member]      
Summary Of Significant Accounting Policies [Line Items]      
Depreciation, depletion and amortization 132,500 116,800 $ 91,000
Other property and equipment [Member]      
Summary Of Significant Accounting Policies [Line Items]      
Depreciation $ 1,800 2,000 1,900
Other property and equipment [Member] | Minimum [Member]      
Summary Of Significant Accounting Policies [Line Items]      
Property and equipment, expected lives 5 years    
Other property and equipment [Member] | Maximum [Member]      
Summary Of Significant Accounting Policies [Line Items]      
Property and equipment, expected lives 40 years    
Proved Oil And Gas Properties [Member] | Marcellus Shale [Member]      
Summary Of Significant Accounting Policies [Line Items]      
Impairment of oil and gas properties     17,700
Unproved Oil And Gas Properties [Member]      
Summary Of Significant Accounting Policies [Line Items]      
Impairment of oil and gas properties $ 27,600 28,300 $ 29,800
Commodity Contract [Member] | Not Designated as Hedging Instrument [Member]      
Summary Of Significant Accounting Policies [Line Items]      
Fair value of commodity derivative contracts $ 5,700 $ (5,100)  
Sales Revenue, Net [Member]      
Summary Of Significant Accounting Policies [Line Items]      
Number of customers | Customer 1 2 4
Revenue From Contract With Customer [Member]      
Summary Of Significant Accounting Policies [Line Items]      
Accounts receivable $ 94,100 $ 52,900  
Unbilled Revenues [Member]      
Summary Of Significant Accounting Policies [Line Items]      
Accounts receivable $ 94,100 $ 52,900