Stock-based compensation - PSU (Details) $ in Thousands	1 Months Ended			2 Months Ended	3 Months Ended		7 Months Ended	9 Months Ended		18 Months Ended
	Feb. 29, 2020 milestone installment shares	Sep. 30, 2019 milestone shares	Oct. 31, 2018 milestone shares	Mar. 31, 2020 shares	Mar. 31, 2020 USD ($) shares	Mar. 31, 2019 USD ($)	Mar. 31, 2020 shares	Mar. 31, 2020 USD ($) shares	Mar. 31, 2019 USD ($)	Mar. 31, 2020 shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense | $					$ 1,959	$ 1,688		$ 5,189	$ 5,611
PSU
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Performance milestones | milestone	4	4	4
Trading days, period	30 days	30 days	30 days
Performance period (in years)	3 years	3 years	3 years
Percentage eligible to vest	25.00%	25.00%	25.00%
Percentage that will vest upon reaching milestone		50.00%	50.00%
Percentage will vest on one year anniversary of performance milestone		50.00%	50.00%
Performance-based RSUs earned (in shares)				0			0	0		0
Stock-based compensation expense | $					$ 528			$ 780
Performance-based RSUs canceled (in shares)								0
Performance-based RSUs outstanding (in shares)				1,300,000	1,300,000		1,300,000	1,300,000		1,300,000
PSU | Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted (in shares)	500,000	560,000	240,000
Number of installments | installment	4