Commitments and contingencies - Lease agreements (Details) $ in Thousands							1 Months Ended			3 Months Ended		6 Months Ended
	Dec. 25, 2020 USD ($)	Jun. 29, 2020 USD ($)	Jun. 24, 2020 USD ($)	Jun. 23, 2020 USD ($)	Oct. 22, 2019 USD ($) ft²	Aug. 01, 2019 USD ($) ft²	Jun. 30, 2019 USD ($) ft²	Jun. 30, 2018 USD ($) ft² Option	Apr. 30, 2016	Sep. 30, 2020 USD ($)	Sep. 30, 2019 USD ($)	Sep. 30, 2020 USD ($)	Sep. 30, 2019 USD ($)	Mar. 31, 2020 USD ($)
Lease agreements
Increase of lease liability and right-of-use asset from lease modification		$ 1,580
Prior notice period upon termination of lease									12 months
Base rent of monthly lease payments	$ 29		$ 14	$ 29
Reclassified from prepaid rent					$ 18,164	$ 2,368
Leased office space | ft²					52,500	10,500	18,700	63,000
Prepaid Rent					$ 261
Lease term							10 years	10 years
Number of options to renewal the lease | Option								2
Renewal period of lease							5 years	5 years
Annual rental payment							$ 488	$ 2,373
Percentage of annual increase in lease rental expenses							1.60%	3.00%
Property, plant and equipment, net										$ 7,166		$ 7,166		$ 6,860
Right-to-use asset							$ 4,363			5,830		5,830		$ 4,425
Right-to-use liability							$ 4,363			6,073		6,073
General and administrative expenses
Lease agreements
Finance Lease Cost										89	$ 60	179	$ 149
Research and development expenses
Lease agreements
Finance Lease Cost										$ 518	$ 0	$ 1,035	$ 0