Property and equipment, net - Narrative (Details)					1 Months Ended	12 Months Ended
	Apr. 04, 2019 USD ($)	Mar. 26, 2019 USD ($)	Feb. 27, 2019 a well	Nov. 02, 2017 USD ($)	Dec. 31, 2017 USD ($) a	Dec. 31, 2019 USD ($) a	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)
Property, Plant and Equipment [Line Items]
DD&A related to oil and natural gas properties						$ 136,200,000	$ 140,400,000	$ 35,400,000
Depreciation and amortization expense						137,937,000	141,815,000	36,091,000
Capitalized costs included in proved oil and natural gas properties not subject to DD&A						19,900,000	87,100,000
Impairment of oil and gas proved properties						0	0	1,061,000
Impairment of oil and gas unproved properties						12,400,000	0	0
Exploratory well costs						0	0
Dry hole costs						0	0	200,000
Payments to acquire businesses						0	4,005,000	114,843,000
Proceeds received		$ 21,800,000		$ 6,500,000		21,770,000	0	6,252,000
Gain on divestiture	$ 11,100,000			$ 5,300,000		11,117,000	(499,000)	4,995,000
Other property and equipment
Property, Plant and Equipment [Line Items]
Depreciation and amortization expense						$ 900,000	700,000	400,000
Exchange and Farm-in Agreement
Property, Plant and Equipment [Line Items]
Area of land received subject to obligation (acres) | a			2,200			935
Drilling and completion costs obligation percentage			25.00%
Drilling and completion obligation, number of wells (up to) | well			7
Series of Individually Immaterial Business Acquisitions
Property, Plant and Equipment [Line Items]
Consideration transferred							$ 15,300,000	$ 6,500,000
White Wolf Acquisition
Property, Plant and Equipment [Line Items]
Consideration transferred					$ 121,100,000
Net acres received in transaction | a					6,505
Payments to acquire businesses					$ 116,600,000
Transaction fees					2,900,000
Increase in abandonment liability					$ 1,600,000