Cash, cash equivalents and short-term investments - Summary of cash, cash equivalents and short-term investments (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Jun. 30, 2019	Dec. 31, 2018
Debt Securities, Available-for-sale [Line Items]
Cash	$ 20,824	$ 25,987
Total cash equivalents	5,523	1,288
Total cash and cash equivalents	26,347	27,275	$ 22,405
Debt securities
Amortized Cost	102,139	70,493
Unrealized Gains	488	404
Unrealized Losses	(24)	(43)
Estimated Fair Value	102,603	70,854
Marketable equity securities
Amortized Cost		250
Unrealized Gains		1,099
Unrealized Losses		0
Estimated Fair Value		1,349
Short-term investments
Amortized Cost		70,743
Unrealized Gains		1,503
Unrealized Losses		(43)
Estimated Fair Value	102,603	72,203
Cash, cash equivalents and short-term investments
Amortized Cost	128,486	98,018
Unrealized Gains	488	1,503
Unrealized Losses	(24)	(43)
Estimated Fair Value	128,950	99,478
U.S. treasury securities
Debt securities
Amortized Cost	2,618	3,570
Unrealized Gains	9	6
Unrealized Losses	0	(4)
Estimated Fair Value	2,627	3,572
U.S. agency securities
Debt securities
Amortized Cost	3,815	3,002
Unrealized Gains	6	9
Unrealized Losses	(2)	(2)
Estimated Fair Value	3,819	3,009
Asset-backed securities
Debt securities
Amortized Cost	20,446	12,319
Unrealized Gains	93	104
Unrealized Losses	(19)	(10)
Estimated Fair Value	20,520	12,413
Municipal securities
Debt Securities, Available-for-sale [Line Items]
Total cash equivalents	750
Debt securities
Amortized Cost	8,930	4,124
Unrealized Gains	27	16
Unrealized Losses	0	0
Estimated Fair Value	8,957	4,140
Commercial paper
Debt securities
Amortized Cost	3,676	1,986
Unrealized Gains	1	0
Unrealized Losses	0	0
Estimated Fair Value	3,677	1,986
Corporate bonds
Debt securities
Amortized Cost	62,654	45,492
Unrealized Gains	352	269
Unrealized Losses	(3)	(27)
Estimated Fair Value	63,003	45,734
Money market mutual funds
Debt Securities, Available-for-sale [Line Items]
Total cash equivalents	4,274	790
Commercial paper
Debt Securities, Available-for-sale [Line Items]
Total cash equivalents	$ 499	$ 498

Cash, Cash Equivalents, And Short-Term Investments, Accumulated Gross Unrealized Gain (Loss) [Abstract]

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Cash, Cash Equivalents And Short-term Investments, Accumulated Gross Unrealized Gains

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Equity Securities, Accumulated Gross Unrealized Gain, Before Tax

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Short-term Investments, Amortized Cost

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Amount, before tax, of unrealized gain in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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Amount, before tax, of unrealized loss in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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Amortized cost of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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Amount of currency on hand as well as demand deposits with banks or financial institutions. Includes other kinds of accounts that have the general characteristics of demand deposits. Also includes short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates. Excludes cash and cash equivalents within disposal group and discontinued operation.

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Cash includes currency on hand as well as demand deposits with banks or financial institutions. It also includes other kinds of accounts that have the general characteristics of demand deposits in that the customer may deposit additional funds at any time and effectively may withdraw funds at any time without prior notice or penalty. Cash equivalents, excluding items classified as marketable securities, include short-term, highly liquid Investments that are both readily convertible to known amounts of cash, and so near their maturity that they present minimal risk of changes in value because of changes in interest rates. Generally, only investments with original maturities of three months or less qualify under that definition. Original maturity means original maturity to the entity holding the investment. For example, both a three-month US Treasury bill and a three-year Treasury note purchased three months from maturity qualify as cash equivalents. However, a Treasury note purchased three years ago does not become a cash equivalent when its remaining maturity is three months. Short-term investments, exclusive of cash equivalents, generally consist of marketable securities intended to be sold within one year (or the normal operating cycle if longer) and may include trading securities, available-for-sale securities, or held-to-maturity securities (if maturing within one year), as applicable.

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Amount of investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI).

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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