Cash, cash equivalents and short-term investments - Summary of cost and estimated fair value of short-term investments (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Jun. 30, 2019
Amortized Cost
Due within one year	$ 36,976
Due between one and two years	36,748
Due between two and three years	15,021
Amortized Cost	88,745	$ 70,493
Estimated Fair Value
Due within one year	37,358
Due between one and two years	37,635
Due between two and three years	15,321
Total	$ 90,314