Employee savings and retirement plan (Details) - USD ($)	12 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2017
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	$ 8,000
Expense recorded for matching contributions	$ 1,100,000	$ 1,300,000	$ 1,300,000