Employee savings and retirement plan (Details) - USD ($) $ in Thousands	12 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2016
Retirement Benefits [Abstract]
Maximum amount of current compensation employees may contributed to their 401(k) plan as percentage of salary	100.00%
Percentage of salary employer matches	4.00%
Maximum annual contribution for each employee	$ 8
Expense recorded for matching contributions	$ 1,300	$ 1,300	$ 1,400