Property and equipment - Benchmark prices and realized prices (Details)	3 Months Ended
	Mar. 31, 2020 $ / MMBTU $ / MMcf $ / bbl	Dec. 31, 2019 $ / MMBTU $ / MMcf $ / bbl	Sep. 30, 2019 $ / MMBTU $ / MMcf $ / bbl	Jun. 30, 2019 $ / MMBTU $ / MMcf $ / bbl	Mar. 31, 2019 $ / MMBTU $ / MMcf $ / bbl
Oil ($/Bbl)
Property, Plant and Equipment [Line Items]
Benchmark Prices (USD per unit)	52.23	52.19	54.27	57.90	59.52
Realized Prices (USD per unit)	52.47	52.12	52.86	55.69	56.72
NGL ($/Bbl)
Property, Plant and Equipment [Line Items]
Benchmark Prices (USD per unit)	19.36	21.14	23.93	28.21	30.34
Realized Prices (USD per unit)	10.47	12.21	14.78	18.64	20.46
Natural gas ($/MMBtu)
Property, Plant and Equipment [Line Items]
Benchmark Prices (USD per unit) | $ / MMBTU	0.58	0.87	0.85	1.14	1.58
Realized Prices (USD per unit) | $ / MMcf	0.28	0.53	0.52	0.70	1.09