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Fair Value Measurements - Additional Information (Detail)
3 Months Ended 9 Months Ended
Sep. 30, 2019
USD ($)
Sep. 30, 2018
USD ($)
Jun. 30, 2018
USD ($)
Mar. 31, 2018
USD ($)
Sep. 30, 2019
USD ($)
Counterparty
Sep. 30, 2018
USD ($)
Dec. 31, 2018
USD ($)
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]              
Interest and dividends $ 197,000 $ 225,000     $ 560,000 $ 606,000  
Mark-to-market gain (loss) (361,000) $ 1,300,000     6,300,000 $ 522,000  
Allowance for doubtful accounts on accounts receivable 4,274,000       $ 4,274,000   $ 6,118,000
Number of derivative counterparties | Counterparty         19    
Number of counter parties that are not participants in bank credit facility | Counterparty         3    
Counterparties not in Facility              
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]              
Net derivative receivable 2,000,000.0       $ 2,000,000.0    
Natural Gas and Oil Properties | Fair Value, Measurements, Nonrecurring              
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]              
Impairment on natural gas and oil properties $ 0       $ 0    
Oklahoma              
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]              
Impairment on natural gas and oil properties       $ 7,300,000      
Oklahoma | Natural Gas and Oil Properties | Fair Value, Measurements, Nonrecurring              
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]              
Fair value       $ 32,500,000      
Northwest Pennsylvania              
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]              
Impairment on natural gas and oil properties     $ 15,300,000        
Fair value     $ 0