Summary of business and significant accounting policies - Leases (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Jul. 01, 2019	Jun. 30, 2019
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Operating lease right-of-use assets	$ 7,909		$ 0
Operating lease liability	$ 8,946
Accounting Standards Update 2016-02
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Operating lease right-of-use assets		$ 11,700
Operating lease liability		$ 13,000