Income Taxes - Difference between Income Taxes Computed At Federal Statutory Rate and Provision for (Benefit from) Income Taxes (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2018
Income Tax Disclosure [Abstract]
Expected benefit at U.S. federal statutory rate									$ (6,518)	$ (1,569)	$ (1,976)
Stock-based compensation									(31,047)	390	297
Federal and state R&D credits, net of unrecognized benefit									(6,411)	(2,111)	(909)
Deferred tax asset re-measurement due to Tax Reform											12,227
Change in valuation allowance									43,716	3,029	(9,753)
Other									313	105	124
Provision for (benefit from) income taxes	$ 1	$ 1	$ 0	$ 51	$ (59)	$ (70)	$ (6)	$ (21)	$ 53	$ (156)	$ 10