Stockholders' equity - Narrative - Stock Repurchase Program (Details) - USD ($)		1 Months Ended	12 Months Ended
		Feb. 28, 2019	Jun. 30, 2019	Jun. 30, 2018	[1]	Jun. 30, 2017	[1]
Equity, Class of Treasury Stock [Line Items]
Authorized repurchase amount		$ 20,000,000.0
Share repurchase program, term		18 months
Payments for stock repurchases			$ 1,303,000	$ 0		$ 0
Number of shares repurchased (in shares)			221,333
Average purchase price per share (in dollars per share)			$ 5.89
Stock repurchases	[2]		$ 1,303,000
Additional Paid-in Capital
Equity, Class of Treasury Stock [Line Items]
Stock repurchases			714,000
Retained Earnings
Equity, Class of Treasury Stock [Line Items]
Stock repurchases	[2]		$ 589,000

[1] See Note 1 for a summary of adjustments.

[2] See Note 1 for a summary of adjustments. The cumulative effect adjustment to Accumulated Deficit and Total Stockholders' Equity related to the adoption of ASU No. 2014-09 (Topic 606) as of June 30, 2016 was $11.8 million.