Commodity Derivative Positions (Detail)	Sep. 30, 2020 bbl $ / bbl
Crude Oil | Swap | Fourth Quarter 2020 [Member]
Derivative Instruments Related to Oil and Gas Production [Line Items]
Derivative, Swap Type, Average Fixed Price	57.59
Derivative, Nonmonetary Notional Amount | bbl	10,174
Crude Oil | Swap | First Quarter 2021 [Domain]
Derivative Instruments Related to Oil and Gas Production [Line Items]
Derivative, Swap Type, Average Fixed Price	55.89
Derivative, Nonmonetary Notional Amount | bbl	3,333
Crude Oil | Swap | Second Quarter 2021 [Domain]
Derivative Instruments Related to Oil and Gas Production [Line Items]
Derivative, Swap Type, Average Fixed Price	55.89
Derivative, Nonmonetary Notional Amount | bbl	3,297
Crude Oil | 2-Way Collars [Domain] | Fourth Quarter 2020 [Member]
Derivative Instruments Related to Oil and Gas Production [Line Items]
Derivative, Average Floor Price	48.00
Derivative, Average Cap Price	57.10
Derivative, Nonmonetary Notional Amount | bbl	2,000
Crude Oil | 2-Way Collars [Domain] | First Quarter 2021 [Domain]
Derivative Instruments Related to Oil and Gas Production [Line Items]
Derivative, Average Floor Price	44.50
Derivative, Average Cap Price	53.53
Derivative, Nonmonetary Notional Amount | bbl	6,667
Crude Oil | 2-Way Collars [Domain] | Second Quarter 2021 [Domain]
Derivative Instruments Related to Oil and Gas Production [Line Items]
Derivative, Average Floor Price	44.50
Derivative, Average Cap Price	53.53
Derivative, Nonmonetary Notional Amount | bbl	6,593
Crude Oil | 2-Way Collars [Domain] | Third Quarter 2021 [Domain]
Derivative Instruments Related to Oil and Gas Production [Line Items]
Derivative, Average Floor Price	40.67
Derivative, Average Cap Price	53.50
Derivative, Nonmonetary Notional Amount | bbl	4,891
Crude Oil | 2-Way Collars [Domain] | Fourth Quarter 2021 [Domain]
Derivative Instruments Related to Oil and Gas Production [Line Items]
Derivative, Average Floor Price	40.67
Derivative, Average Cap Price	53.50
Derivative, Nonmonetary Notional Amount | bbl	4,891
Crude Oil | Put Option | Fourth Quarter 2020 [Member]
Derivative Instruments Related to Oil and Gas Production [Line Items]
Derivative, Swap Type, Average Fixed Price	43.55
Derivative, Nonmonetary Notional Amount | bbl	3,783
Crude Oil | Put Option | First Quarter 2021 [Domain]
Derivative Instruments Related to Oil and Gas Production [Line Items]
Derivative, Swap Type, Average Fixed Price	36.93
Derivative, Nonmonetary Notional Amount | bbl	11,667
Crude Oil | Put Option | Second Quarter 2021 [Domain]
Derivative Instruments Related to Oil and Gas Production [Line Items]
Derivative, Swap Type, Average Fixed Price	36.93
Derivative, Nonmonetary Notional Amount | bbl	11,538
Crude Oil | Put Option | Third Quarter 2021 [Domain]
Derivative Instruments Related to Oil and Gas Production [Line Items]
Derivative, Swap Type, Average Fixed Price	35.00
Derivative, Nonmonetary Notional Amount | bbl	4,891
Crude Oil | Put Option | Fourth Quarter 2021 [Domain]
Derivative Instruments Related to Oil and Gas Production [Line Items]
Derivative, Swap Type, Average Fixed Price	35.00
Derivative, Nonmonetary Notional Amount | bbl	4,891
Crude Oil | Basis Swap [Domain] | Fourth Quarter 2020 [Member]
Derivative Instruments Related to Oil and Gas Production [Line Items]
Derivative, Swap Type, Average Fixed Price	1.31
Derivative, Nonmonetary Notional Amount | bbl	6,348
Crude Oil | CMA Roll Basis Swap [Domain] | Fourth Quarter 2020 [Member]
Derivative Instruments Related to Oil and Gas Production [Line Items]
Derivative, CMA Roll Basis Swap, Price	(0.42)
Derivative, Nonmonetary Notional Amount | bbl	2,174
Natural Gas [Member] | 2-Way Collars [Domain] | Fourth Quarter 2020 [Member]
Derivative Instruments Related to Oil and Gas Production [Line Items]
Derivative, Average Floor Price	2.00
Derivative, Average Cap Price	2.21
Derivative, Nonmonetary Notional Amount | bbl	12,804
Natural Gas [Member] | 2-Way Collars [Domain] | First Quarter 2021 [Domain]
Derivative Instruments Related to Oil and Gas Production [Line Items]
Derivative, Average Floor Price	2.61
Derivative, Average Cap Price	3.12
Derivative, Nonmonetary Notional Amount | bbl	10,000
Natural Gas [Member] | 2-Way Collars [Domain] | Second Quarter 2021 [Domain]
Derivative Instruments Related to Oil and Gas Production [Line Items]
Derivative, Average Floor Price	2.61
Derivative, Average Cap Price	3.12
Derivative, Nonmonetary Notional Amount | bbl	9,890
Natural Gas [Member] | 2-Way Collars [Domain] | Third Quarter 2021 [Domain]
Derivative Instruments Related to Oil and Gas Production [Line Items]
Derivative, Average Floor Price	2.61
Derivative, Average Cap Price	3.12
Derivative, Nonmonetary Notional Amount | bbl	9,783
Natural Gas [Member] | 2-Way Collars [Domain] | Fourth Quarter 2021 [Domain]
Derivative Instruments Related to Oil and Gas Production [Line Items]
Derivative, Average Floor Price	2.61
Derivative, Average Cap Price	3.12
Derivative, Nonmonetary Notional Amount | bbl	9,783
Natural Gas [Member] | Put Option | First Quarter 2021 [Domain]
Derivative Instruments Related to Oil and Gas Production [Line Items]
Derivative, Swap Type, Average Fixed Price	2.00
Derivative, Nonmonetary Notional Amount | bbl	6,667
Natural Gas [Member] | Put Option | Second Quarter 2021 [Domain]
Derivative Instruments Related to Oil and Gas Production [Line Items]
Derivative, Swap Type, Average Fixed Price	2.00
Derivative, Nonmonetary Notional Amount | bbl	6,593
Natural Gas [Member] | Put Option | Third Quarter 2021 [Domain]
Derivative Instruments Related to Oil and Gas Production [Line Items]
Derivative, Swap Type, Average Fixed Price	2.00
Derivative, Nonmonetary Notional Amount | bbl	6,522
Natural Gas [Member] | Put Option | Fourth Quarter 2021 [Domain]
Derivative Instruments Related to Oil and Gas Production [Line Items]
Derivative, Swap Type, Average Fixed Price	2.00
Derivative, Nonmonetary Notional Amount | bbl	6,522