Stock-based compensation - Employee Stock Purchase Plans (Details) $ / shares in Units, $ in Thousands		3 Months Ended
	Nov. 20, 2019 period shares	Sep. 30, 2020 USD ($) $ / shares shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Proceeds from employee stock purchase		$ 1,204
ESPP
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
ESPP shares authorized (in shares) | shares	2,500,000
Offering period	12 months
Number of purchase periods | period	2
ESPP share purchase price, percent	85.00%
Common stock purchased (in shares) | shares		304,964
Weighted average purchase price (in dollars per share) | $ / shares		$ 3.94
Proceeds from employee stock purchase		$ 1,200
Unrecognized stock-based compensation expense		$ 1,600
Average vesting period		7 months 20 days