Nature of the business and basis of presentation - Initial public offering (Details) $ / shares in Units, $ in Millions			1 Months Ended	3 Months Ended
	May 28, 2019 shares	Mar. 28, 2019 $ / shares shares	Jun. 30, 2019 shares	Mar. 31, 2020 USD ($)
IPO
Share capital reorganization and share split
Shares issued (in shares) | shares		4,333,333
Share issue price | $ / shares		$ 14.00
Proceeds from IPO, net | $				$ 56.4
Underwriting discounts and commissions | $				4.5
Offering expenses | $				$ 4.0
IPO | Ordinary Shares
Share capital reorganization and share split
Conversion of convertible preferred shares to ordinary shares (in shares) | shares	11,647,529
Conversion ratio	0.6997
Over allotment option
Share capital reorganization and share split
Shares issued (in shares) | shares			304,333