Acquisitions and divestiture of evaluated and unevaluated oil and natural gas properties - Narrative (Details) $ in Millions					12 Months Ended
	Feb. 04, 2020 USD ($) a	Dec. 12, 2019 USD ($) a	Dec. 06, 2019 USD ($) a Boe property	Jun. 20, 2019 USD ($) a	Dec. 31, 2020 USD ($) $ / bbl
Howard County Net Acres
Business Acquisition [Line Items]
Area of land (in acres) | a	80
Howard County Net Acres
Business Acquisition [Line Items]
Consideration transferred in acquisition | $	$ 22.5	$ 131.7
Area of land (in acres) | a	1,180	7,360
Fair value of contingent consideration | $		$ 6.2
Howard County Net Acres | Forecast | WTI NYMEX | Not designated as hedges | Oil put: January 2020 - December 2020 | Crude Oil
Business Acquisition [Line Items]
Notional amount of derivative | $					$ 20.0
Contingent consideration trigger (USD per bbl) | $ / bbl					60.00
Howard County Net Royalty Acres
Business Acquisition [Line Items]
Area of land (in acres) | a		750
Reagan County Net Acres
Business Acquisition [Line Items]
Consideration transferred in acquisition | $				$ 2.9
Area of land (in acres) | a				640
Acquired evaluated and unevaluated oil and natural gas properties in Glasscock County, Texas
Business Acquisition [Line Items]
Area of land (in acres) | a			4,475
Production reserve (BOE per day) | Boe			1,400
Agreed purchase price | $			$ 64.6
Leasehold interests and Working interests
Business Acquisition [Line Items]
Number of real estate properties | property			49