Derivative Instruments - Summary of Derivative Instrument Positions for Future Production Periods (Detail)	9 Months Ended
	Sep. 30, 2020 MMBTU $ / MMBTU $ / bbl bbl
Natural Gas Swaps Production Period October 2020 - December 2020 [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Volume (MMBtu/d) \| MMBTU	130,000
Weighted Average Price \| $ / MMBTU	2.42
Natural Gas Swaps Production Period October 2020 - March 2021 [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Volume (MMBtu/d) \| MMBTU	145,000
Weighted Average Price \| $ / MMBTU	2.58
Natural Gas Swaps Production Period January 2021 - March 2022 [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Volume (MMBtu/d) \| MMBTU	50,000
Weighted Average Price \| $ / MMBTU	2.51
Natural Gas Swaps Production Period April 2021 - March 2022 [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Volume (MMBtu/d) \| MMBTU	25,000
Weighted Average Price \| $ / MMBTU	2.47
Basis Swaps Production Period October 2020 [Member] \| Appalachia [Member] \| Dominion Resources, Inc [Member] \| Swap [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Volume (MMBtu/d) \| MMBTU	42,500
Weighted Average Price ($/MMBtu) \| $ / MMBTU	(0.51)
Basis Swaps Production Period October 2020 - December 2020 [Member] \| Appalachia [Member] \| Dominion Resources, Inc [Member] \| Swap [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Volume (MMBtu/d) \| MMBTU	20,000
Weighted Average Price ($/MMBtu) \| $ / MMBTU	(0.59)
Natural Gas Collars Production Period January 2021 - December 2021 [Member] \| Put Option \| Purchase [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Volume (MMBtu/d) \| MMBTU	25,000
Weighted Average Price, Floor \| $ / MMBTU	2.15
Natural Gas Collars Production Period January 2021 - December 2021 [Member] \| Call Option [Member] \| Sold [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Volume (MMBtu/d) \| MMBTU	25,000
Weighted Average Price, Ceiling \| $ / MMBTU	3.03
Natural Gas Collars Production Period April 2021 - March 2022 [Member] \| Put Option \| Purchase [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Volume (MMBtu/d) \| MMBTU	30,000
Weighted Average Price, Floor \| $ / MMBTU	2.40
Natural Gas Collars Production Period April 2021 - March 2022 [Member] \| Call Option [Member] \| Sold [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Volume (MMBtu/d) \| MMBTU	30,000
Weighted Average Price, Ceiling \| $ / MMBTU	3.05
Natural Gas Collars Production Period August 2021 - December 2021 [Member] \| Put Option \| Purchase [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Volume (MMBtu/d) \| MMBTU	15,000
Weighted Average Price, Floor \| $ / MMBTU	2.55
Natural Gas Collars Production Period August 2021 - December 2021 [Member] \| Call Option [Member] \| Sold [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Volume (MMBtu/d) \| MMBTU	15,000
Weighted Average Price, Ceiling \| $ / MMBTU	3.13
Natural Gas Collars Production Period September 2021 - November 2021 [Member] \| Put Option \| Purchase [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Volume (MMBtu/d) \| MMBTU	15,000
Weighted Average Price, Floor \| $ / MMBTU	2.52
Natural Gas Collars Production Period September 2021 - November 2021 [Member] \| Call Option [Member] \| Sold [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Volume (MMBtu/d) \| MMBTU	15,000
Weighted Average Price, Ceiling \| $ / MMBTU	3.12
Natural Gas Collars Production Period August 2021 [Member] \| Put Option \| Purchase [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Volume (MMBtu/d) \| MMBTU	5,000
Weighted Average Price, Floor \| $ / MMBTU	2.50
Natural Gas Collars Production Period August 2021 [Member] \| Call Option [Member] \| Sold [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Volume (MMBtu/d) \| MMBTU	5,000
Weighted Average Price, Ceiling \| $ / MMBTU	3.05
Natural Gas Collars Production Period September 2021 [Member] \| Put Option \| Purchase [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Volume (MMBtu/d) \| MMBTU	10,000
Weighted Average Price, Floor \| $ / MMBTU	2.50
Natural Gas Collars Production Period September 2021 [Member] \| Call Option [Member] \| Sold [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Volume (MMBtu/d) \| MMBTU	10,000
Weighted Average Price, Ceiling \| $ / MMBTU	3.03
Natural Gas Three-way Collars Production Period October 2020 - December 2020 [Member] \| Put Option \| Sold [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Volume (MMBtu/d) \| MMBTU	80,000
Weighted Average Price, Floor \| $ / MMBTU	1.90
Natural Gas Three-way Collars Production Period October 2020 - December 2020 [Member] \| Put Option \| Purchase [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Volume (MMBtu/d) \| MMBTU	80,000
Weighted Average Price, Floor \| $ / MMBTU	2.60
Natural Gas Three-way Collars Production Period October 2020 - December 2020 [Member] \| Call Option [Member] \| Sold [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Volume (MMBtu/d) \| MMBTU	80,000
Weighted Average Price, Ceiling \| $ / MMBTU	2.94
Natural Gas Three-way Collars Production Period January 2021 - December 2021 [Member] \| Put Option \| Sold [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Volume (MMBtu/d) \| MMBTU	45,000
Weighted Average Price, Floor \| $ / MMBTU	2.25
Natural Gas Three-way Collars Production Period January 2021 - December 2021 [Member] \| Put Option \| Purchase [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Volume (MMBtu/d) \| MMBTU	45,000
Weighted Average Price, Floor \| $ / MMBTU	2.55
Natural Gas Three-way Collars Production Period January 2021 - December 2021 [Member] \| Call Option [Member] \| Sold [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Volume (MMBtu/d) \| MMBTU	45,000
Weighted Average Price, Ceiling \| $ / MMBTU	2.81
Natural Gas Three-way Collars Production Period April 2021 - March 2022 [Member] \| Put Option \| Sold [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Volume (MMBtu/d) \| MMBTU	20,000
Weighted Average Price, Floor \| $ / MMBTU	2.20
Natural Gas Three-way Collars Production Period April 2021 - March 2022 [Member] \| Put Option \| Purchase [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Volume (MMBtu/d) \| MMBTU	20,000
Weighted Average Price, Floor \| $ / MMBTU	2.62
Natural Gas Three-way Collars Production Period April 2021 - March 2022 [Member] \| Call Option [Member] \| Sold [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Volume (MMBtu/d) \| MMBTU	20,000
Weighted Average Price, Ceiling \| $ / MMBTU	3.10
Natural Gas Call/Put Options Production Period October 2020 - December 2020 [Member] \| Put Option \| Sold [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Volume (MMBtu/d) \| MMBTU	50,000
Weighted Average Price \| $ / MMBTU	2.30
Natural Gas Call/Put Options Production Period January 2021 - December 2021 [Member] \| Call Option [Member] \| Sold [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Volume (MMBtu/d) \| MMBTU	50,000
Weighted Average Price \| $ / MMBTU	2.75
Natural Gas Call/Put Options Production Period January 2022 - December 2022 [Member] \| Call Option [Member] \| Sold [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Volume (MMBtu/d) \| MMBTU	50,000
Weighted Average Price \| $ / MMBTU	3.00
Natural Gas Call/Put Options Production Period January 2022 - December 2022 [Member] \| Call Option [Member] \| Sold [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Volume (MMBtu/d) \| MMBTU	50,000
Weighted Average Price \| $ / MMBTU	3.00
Natural Gas Call/Put Options Production Period January 2021 - March 2022 [Member] \| Put Option \| Sold [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Volume (MMBtu/d) \| MMBTU	50,000
Weighted Average Price \| $ / MMBTU	2.00
Natural Gas Call/Put Options Production Period January 2023 - December 2023 [Member] \| Call Option [Member] \| Sold [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Volume (MMBtu/d) \| MMBTU	80,000
Weighted Average Price \| $ / MMBTU	3.00
Oil Swaps Production Period October 2020 - December 2020 [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Weighted Average Price \| $ / bbl	57.41
Volume (Bbls/d) \| bbl	2,500
Oil Swaps Production Period October 2020 - March 2021 [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Weighted Average Price \| $ / bbl	53.20
Volume (Bbls/d) \| bbl	250
Oil Swaps Production Period January 2021 - March 2021 [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Weighted Average Price \| $ / bbl	53.00
Volume (Bbls/d) \| bbl	250
Oil Swaps Production Period January 2021 [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Weighted Average Price \| $ / bbl	43.60
Volume (Bbls/d) \| bbl	100
Oil Collars Production Period October 2020 - December 2020 [Member] \| Put Option \| Purchase [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Weighted Average Price, Floor \| $ / bbl	51.00
Volume (Bbls/d) \| bbl	1,000
Oil Collars Production Period October 2020 - December 2020 [Member] \| Call Option [Member] \| Sold [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Weighted Average Price, Ceiling \| $ / bbl	62.00
Volume (Bbls/d) \| bbl	1,000
Oil Collars Production Period January 2021 - December 2021 [Member] \| Put Option \| Purchase [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Weighted Average Price, Floor \| $ / bbl	37.50
Volume (Bbls/d) \| bbl	500
Oil Collars Production Period January 2021 - December 2021 [Member] \| Call Option [Member] \| Sold [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Weighted Average Price, Ceiling \| $ / bbl	45.50
Volume (Bbls/d) \| bbl	500
Oil Collars Production Period April 2021 [Member] \| Put Option \| Purchase [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Weighted Average Price, Floor \| $ / bbl	40.00
Volume (Bbls/d) \| bbl	300
Oil Collars Production Period April 2021 [Member] \| Call Option [Member] \| Sold [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Weighted Average Price, Ceiling \| $ / bbl	47.25
Volume (Bbls/d) \| bbl	300
Oil Collars Production Period May 2021 [Member] \| Put Option \| Purchase [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Weighted Average Price, Floor \| $ / bbl	40.00
Volume (Bbls/d) \| bbl	200
Oil Collars Production Period May 2021 [Member] \| Call Option [Member] \| Sold [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Weighted Average Price, Ceiling \| $ / bbl	47.55
Volume (Bbls/d) \| bbl	200
Oil Collars Production Period June 2021 [Member] \| Put Option \| Purchase [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Weighted Average Price, Floor \| $ / bbl	40.00
Volume (Bbls/d) \| bbl	100
Oil Collars Production Period June 2021 [Member] \| Call Option [Member] \| Sold [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Weighted Average Price, Ceiling \| $ / bbl	47.75
Volume (Bbls/d) \| bbl	100
Oil Three-way Collars Production Period January 2021 - December 2021 [Member] \| Put Option \| Sold [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Weighted Average Price, Floor \| $ / bbl	22.50
Volume (Bbls/d) \| bbl	500
Oil Three-way Collars Production Period January 2021 - December 2021 [Member] \| Put Option \| Purchase [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Weighted Average Price, Floor \| $ / bbl	31.25
Volume (Bbls/d) \| bbl	500
Oil Three-way Collars Production Period January 2021 - December 2021 [Member] \| Call Option [Member] \| Sold [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Weighted Average Price, Ceiling \| $ / bbl	45.00
Volume (Bbls/d) \| bbl	500
Oil Call/Put Option Production Period October 2020 - December 2020 [Member] \| Put Option \| Sold [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Weighted Average Price \| $ / bbl	45.00
Volume (Bbls/d) \| bbl	500
Oil Call/Put Option Production Period January 2021 - December 2021 [Member] \| Call Option [Member] \| Sold [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Weighted Average Price \| $ / bbl	42.50
Volume (Bbls/d) \| bbl	500
Propane Swaps Production Period October 2020 - December 2020 [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Weighted Average Price \| $ / bbl	20.94
Volume (Bbls/d) \| bbl	2,000
Propane Swaps Production Period January 2021 - December 2021 [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Weighted Average Price \| $ / bbl	18.87
Volume (Bbls/d) \| bbl	1,000

Montage Resources Corp 10-Q