Cash, cash equivalents and short-term investments - Summary of Fair Value and Unrealized Loss Position (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Jun. 30, 2018
Marketable Securities [Line Items]
Less than 12 Months, Fair Value	$ 5,093
12 Months or Greater, Fair Value	22,142
Total, Fair Value	27,235
Less than 12 Months, Unrealized Losses	(4)
12 Months or Greater, Unrealized Losses	(41)
Total, Unrealized Losses	(45)
Less than 12 Months, Fair Value		$ 49,136
12 Months or Greater, Fair Value		13,732
Total, Fair Value		62,868
Less than 12 Months, Unrealized Losses		(431)
12 Months or Greater, Unrealized Losses		(130)
Total, Unrealized Losses		(561)
U.S. treasury securities
Marketable Securities [Line Items]
Less than 12 Months, Fair Value	0
12 Months or Greater, Fair Value	2,992
Total, Fair Value	2,992
Less than 12 Months, Unrealized Losses	0
12 Months or Greater, Unrealized Losses	(5)
Total, Unrealized Losses	(5)
Less than 12 Months, Fair Value		4,703
12 Months or Greater, Fair Value		0
Total, Fair Value		4,703
Less than 12 Months, Unrealized Losses		(34)
12 Months or Greater, Unrealized Losses		0
Total, Unrealized Losses		(34)
Commercial paper
Marketable Securities [Line Items]
Less than 12 Months, Fair Value	0
12 Months or Greater, Fair Value	998
Total, Fair Value	998
Less than 12 Months, Unrealized Losses	0
12 Months or Greater, Unrealized Losses	(1)
Total, Unrealized Losses	(1)
Less than 12 Months, Fair Value		1,118
12 Months or Greater, Fair Value		1,290
Total, Fair Value		2,408
Less than 12 Months, Unrealized Losses		(6)
12 Months or Greater, Unrealized Losses		(10)
Total, Unrealized Losses		(16)
Asset-backed securities
Marketable Securities [Line Items]
Less than 12 Months, Fair Value	0
12 Months or Greater, Fair Value	3,537
Total, Fair Value	3,537
Less than 12 Months, Unrealized Losses	0
12 Months or Greater, Unrealized Losses	(11)
Total, Unrealized Losses	(11)
Less than 12 Months, Fair Value		5,368
12 Months or Greater, Fair Value		1,562
Total, Fair Value		6,930
Less than 12 Months, Unrealized Losses		(69)
12 Months or Greater, Unrealized Losses		(3)
Total, Unrealized Losses		(72)
Municipal securities
Marketable Securities [Line Items]
Less than 12 Months, Fair Value		1,716
12 Months or Greater, Fair Value		0
Total, Fair Value		1,716
Less than 12 Months, Unrealized Losses		(4)
12 Months or Greater, Unrealized Losses		0
Total, Unrealized Losses		(4)
Commercial paper
Marketable Securities [Line Items]
Less than 12 Months, Fair Value	493
12 Months or Greater, Fair Value	0
Total, Fair Value	493
Less than 12 Months, Unrealized Losses	(1)
12 Months or Greater, Unrealized Losses	0
Total, Unrealized Losses	(1)
Less than 12 Months, Fair Value		1,249
12 Months or Greater, Fair Value		0
Total, Fair Value		1,249
Less than 12 Months, Unrealized Losses		0
12 Months or Greater, Unrealized Losses		0
Total, Unrealized Losses		0
Corporate bonds
Marketable Securities [Line Items]
Less than 12 Months, Fair Value	4,600
12 Months or Greater, Fair Value	14,615
Total, Fair Value	19,215
Less than 12 Months, Unrealized Losses	(3)
12 Months or Greater, Unrealized Losses	(24)
Total, Unrealized Losses	$ (27)
Less than 12 Months, Fair Value		34,982
12 Months or Greater, Fair Value		10,880
Total, Fair Value		45,862
Less than 12 Months, Unrealized Losses		(318)
12 Months or Greater, Unrealized Losses		(117)
Total, Unrealized Losses		$ (435)