Income taxes - Narrative (Details) - USD ($)	12 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2018
Operating Loss Carryforwards [Line Items]
Provision for income taxes	$ 1,336,000	$ 1,376,000	$ 1,012,000
Effective tax rate (in percent)	30.00%	6.00%
Deferred tax assets	$ 84,554,000	$ 89,783,000
Deferred tax liability	36,260,000	40,649,000
Net deferred tax assets	1,490,000	764,000
Increase (decrease) in valuation allowance	(1,600,000)	(19,300,000)	13,900,000
Earnings of foreign subsidiaries that are permanently reinvested and no U.S. income taxes have been provided	5,000,000.0
Unrecognized deferred tax liability related to undistributed foreign earnings	229,000
Unrecognized tax benefits that if recognized would affect the annual effective tax rate	100,000	100,000	100,000
Unrecognized tax benefits - interest and penalties expense	0	0	$ 15,000
Unrecognized tax benefits - interest and penalties accrued	0	$ 0
Foreign Tax Authority
Operating Loss Carryforwards [Line Items]
Deferred tax assets	1,500,000
Deferred tax liability	25,000
Net deferred tax assets	1,500,000
Net operating loss carryforwards	2,700,000
Internal Revenue Service (IRS)
Operating Loss Carryforwards [Line Items]
Net operating loss carryforwards	167,800,000
Operating loss carry forwards subject to expiration	33,200,000
Operating loss carry forwards not subject to expiration	134,500,000
Internal Revenue Service (IRS) | Research Tax Credit Carryforward
Operating Loss Carryforwards [Line Items]
Research and development tax credit carryforwards	8,100,000
State and Local Jurisdiction
Operating Loss Carryforwards [Line Items]
Net operating loss carryforwards	11,100,000
State and Local Jurisdiction | Research Tax Credit Carryforward
Operating Loss Carryforwards [Line Items]
Research and development tax credit carryforwards	12,900,000
Valuation Allowance, Operating Loss Carryforwards
Operating Loss Carryforwards [Line Items]
Increase (decrease) in valuation allowance	$ 400,000