Fair Value Measurements - Additional Information (Detail)	1 Months Ended	3 Months Ended			9 Months Ended		12 Months Ended
	Aug. 31, 2020 USD ($)	Sep. 30, 2020 USD ($)	Mar. 31, 2020 USD ($)	Sep. 30, 2019 USD ($)	Sep. 30, 2020 USD ($) Counterparty	Sep. 30, 2019 USD ($)	Dec. 31, 2019 USD ($)
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Interest and dividends		$ 114,000		$ 197,000	$ 385,000	$ 560,000
Mark-to-market gain (loss)		3,200,000		$ (361,000)	234,000	6,300,000
Allowance for doubtful accounts on accounts receivable		3,004,000			$ 3,004,000		$ 8,784,000
Number of derivative counterparties | Counterparty					21
Number of counter parties that are not participants in bank credit facility | Counterparty					2
Counterparties not in Facility
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Net derivative asset		(2,200,000)			$ (2,200,000)
One Counterparty Not in Facility
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Net derivative asset		$ 3,300,000			3,300,000
Level 2 | Leases
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Impairment of proved properties and other assets					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 of proved properties and other assets						$ 0
North Louisiana | Level 2
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Impairment of proved properties and other assets			$ 77,000,000.0
North Louisiana | Fair Value, Measurements, Nonrecurring
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Impairment of proved properties and other assets							$ 1,093,531,000
Maximum | North Louisiana | Contingent Consideration
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Potential contractual payout of contingent consideration	$ 90,000,000.0				$ 90,000,000.0
Measurement Input, Price Volatility | Minimum [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Implied volatilities					21.00%
Measurement Input, Price Volatility | Maximum
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Implied volatilities					32.00%
Measurement Input, Price Volatility | Weighted Average
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Implied volatilities					26.00%