Stockholders' equity - Narrative - Performance-based RSUs (Details) $ in Thousands	1 Months Ended			5 Months Ended	10 Months Ended	12 Months Ended			21 Months Ended
	Feb. 29, 2020 milestone installment shares	Sep. 30, 2019 milestone shares	Oct. 31, 2018 milestone shares	Jun. 30, 2020 shares	Jun. 30, 2020 shares	Jun. 30, 2020 USD ($) shares	Jun. 30, 2019 USD ($)	Jun. 30, 2018 USD ($)	Jun. 30, 2020 shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense | $						$ 8,034	$ 7,404	$ 8,768
RSUs outstanding (in shares)				2,476,000	2,476,000	2,476,000			2,476,000
Performance-based RSUs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of performance milestones | milestone	4	4	4
Trading days, period	30 days	30 days	30 days
Performance period (in 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
Stock-based compensation expense | $						$ 2,000
RSUs outstanding (in shares)				1,300,000	1,300,000	1,300,000			1,300,000
Performance-based RSUs | Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Performance period (in years)		3 years
Performance-based RSUs | Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted (in shares)	500,000	560,000	240,000			560,000
Performance period (in years)		4 years
Number of installments | installment	4