Fair value of financial instruments (Details) - USD ($)	12 Months Ended
	Jun. 30, 2019	Jun. 30, 2018		Jun. 30, 2017
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents, fair value	$ 1,288,000	$ 6,915,000
Debt securities, fair value	70,854,000
Estimated Fair Value	1,349,000
Estimated Fair Value	72,203,000	67,829,000	[1]
Cash equivalents and short-term investments	73,491,000	74,744,000
Accretion of net premium on short-term investments	(30,000)	192,000	[1]	$ 403,000	[1]
Non-marketable equity investments under cost method		708,000
Unrealized gain on securities	1,100,000
Carrying value of non-marketable equity securities	458,000	0		$ 0
Money market mutual funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents, fair value	790,000	3,751,000
Commercial paper
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents, fair value	498,000	2,666,000
Debt securities, fair value	3,009,000
Short-term investments, fair value		2,408,000
U.S. treasury securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents, fair value		498,000
Debt securities, fair value	3,572,000
Short-term investments, fair value		4,703,000
Asset-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities, fair value	12,413,000
Short-term investments, fair value		7,969,000
Municipal securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities, fair value	4,140,000
Short-term investments, fair value		2,216,000
Commercial paper
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities, fair value	1,986,000
Short-term investments, fair value		1,249,000
Corporate bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities, fair value	45,734,000
Short-term investments, fair value		49,284,000
Quoted Prices in Active Markets for Identical Assets (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents, fair value	790,000	4,249,000
Debt securities, fair value	3,572,000
Estimated Fair Value	1,349,000
Estimated Fair Value	4,921,000	4,703,000
Cash equivalents and short-term investments	5,711,000	8,952,000
Quoted Prices in Active Markets for Identical Assets (Level 1) | Money market mutual funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents, fair value	790,000	3,751,000
Quoted Prices in Active Markets for Identical Assets (Level 1) | Commercial paper
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents, fair value	0	0
Debt securities, fair value	0
Short-term investments, fair value		0
Quoted Prices in Active Markets for Identical Assets (Level 1) | U.S. treasury securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents, fair value		498,000
Debt securities, fair value	3,572,000
Short-term investments, fair value		4,703,000
Quoted Prices in Active Markets for Identical Assets (Level 1) | Asset-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities, fair value	0
Short-term investments, fair value		0
Quoted Prices in Active Markets for Identical Assets (Level 1) | Municipal securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities, fair value	0
Short-term investments, fair value		0
Quoted Prices in Active Markets for Identical Assets (Level 1) | Commercial paper
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities, fair value	0
Short-term investments, fair value		0
Quoted Prices in Active Markets for Identical Assets (Level 1) | Corporate bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities, fair value	0
Short-term investments, fair value		0
Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents, fair value	498,000	2,666,000
Debt securities, fair value	67,282,000
Estimated Fair Value	0
Estimated Fair Value	67,282,000	63,126,000
Cash equivalents and short-term investments	67,780,000	65,792,000
Significant Other Observable Inputs (Level 2) | Money market mutual funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents, fair value	0	0
Significant Other Observable Inputs (Level 2) | Commercial paper
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents, fair value	498,000	2,666,000
Debt securities, fair value	3,009,000
Short-term investments, fair value		2,408,000
Significant Other Observable Inputs (Level 2) | U.S. treasury securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents, fair value		0
Debt securities, fair value	0
Short-term investments, fair value		0
Significant Other Observable Inputs (Level 2) | Asset-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities, fair value	12,413,000
Short-term investments, fair value		7,969,000
Significant Other Observable Inputs (Level 2) | Municipal securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities, fair value	4,140,000
Short-term investments, fair value		2,216,000
Significant Other Observable Inputs (Level 2) | Commercial paper
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities, fair value	1,986,000
Short-term investments, fair value		1,249,000
Significant Other Observable Inputs (Level 2) | Corporate bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities, fair value	45,734,000
Short-term investments, fair value		49,284,000
Significant Unobservable Inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents, fair value	0	0
Debt securities, fair value	0
Estimated Fair Value	0
Estimated Fair Value	0	0
Cash equivalents and short-term investments	0	0
Significant Unobservable Inputs (Level 3) | Money market mutual funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents, fair value	0	0
Significant Unobservable Inputs (Level 3) | Commercial paper
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents, fair value	0	0
Debt securities, fair value	0
Short-term investments, fair value		0
Significant Unobservable Inputs (Level 3) | U.S. treasury securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents, fair value		0
Debt securities, fair value	0
Short-term investments, fair value		0
Significant Unobservable Inputs (Level 3) | Asset-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities, fair value	0
Short-term investments, fair value		0
Significant Unobservable Inputs (Level 3) | Municipal securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities, fair value	0
Short-term investments, fair value		0
Significant Unobservable Inputs (Level 3) | Commercial paper
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities, fair value	0
Short-term investments, fair value		0
Significant Unobservable Inputs (Level 3) | Corporate bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities, fair value	$ 0
Short-term investments, fair value		$ 0

[1] See Note 1 for a summary of adjustments.