Stock-based compensation - Additional Information (Details)	6 Months Ended
	Jun. 30, 2020 USD ($) Offering $ / shares shares
Unrecognized stock-based compensation cost | $	$ 12,600
Unrecognized stock-based compensation cost, weighted-average period recognized	3 years 21 days
Options granted, Number of Shares | shares	711,700
Options granted, Weighted Average Exercise Price	$ 10.58
Common stock shares reserved for issuance under employee stock purchase plan | shares	759,936
Employee stock ownership plan (ESOP), plan description	eligible employees to contribute, through payroll deductions, up to 15% of their earnings for the purchase of the Company’s shares of common stock at the lower of 85% of the closing price of the Company’s common stock on the first trading day of the offering period or 85% of the closing price of the Company’s common stock on the last trading day of the offering period
employee stock purchase plan number of offering per year | Offering	2
employee stock purchase plan offering commencement date	May 16, 2020
Restricted Stock Units (RSUs) [Member]
Restricted shares Granted | shares	75,000
Restricted stock units granted, Weighted Average Grant Date Fair Value	$ 6.44
Employee Director [Member]
Options granted, Number of Shares | shares	536,700
Employee Director [Member] | Restricted Stock Units (RSUs) [Member]
Restricted shares Granted | shares	75,000
Restricted stock units granted, Weighted Average Grant Date Fair Value	$ 6.44
Employee Director [Member] | Minimum [Member]
Options granted, Weighted Average Exercise Price	6.44
Employee Director [Member] | Maximum [Member]
Options granted, Weighted Average Exercise Price	$ 13.58
Non employee directors [Member]
Options granted, Number of Shares | shares	175,000
Non employee directors [Member] | Minimum [Member]
Options granted, Weighted Average Exercise Price	$ 12.84
Non employee directors [Member] | Maximum [Member]
Options granted, Weighted Average Exercise Price	$ 13.58