Fair Value of Financial Instruments and Investments - Schedule of Major Category of Company's Financial Assets and Liabilities Measured at Fair Value on Recurring Basis (Detail) - Fair Value on a Recurring Basis [Member] - USD ($) $ in Thousands	Jun. 30, 2020	Jun. 30, 2019
Fair Value Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, fair value	$ 80,509	$ 82,073
Cash and Cash Equivalents [Member]
Fair Value Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, fair value	38,463	26,703
US Treasury Securities [Member]
Fair Value Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, fair value	42,046	55,370
Quoted Prices in Active markets (Level 1) [Member]
Fair Value Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, fair value	80,509	82,073
Quoted Prices in Active markets (Level 1) [Member] | Cash and Cash Equivalents [Member]
Fair Value Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, fair value	38,463	26,703
Quoted Prices in Active markets (Level 1) [Member] | US Treasury Securities [Member]
Fair Value Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, fair value	$ 42,046	$ 55,370