Income Taxes - Net Deferred Tax Assets and Liabilities (Detail) - USD ($) $ in Thousands	Sep. 30, 2019	Sep. 30, 2018
Deferred tax assets:
Share-based compensation	$ 9,901	$ 7,372
Other temporary differences	915	828
Accrued compensation	821	696
Tax credit carryforwards	763
Accrued expenses	150	60
Capitalized research and development expenses		223
Unrealized loss		139
Total deferred tax assets	12,550	9,318
Net deferred tax assets	12,550	9,318
Deferred tax liabilities:
Depreciation	(1,027)	(798)
Prepaid expenses	(148)	(145)
Unrealized gain	(34)
Total deferred tax liabilities	(1,209)	(943)
Net deferred income tax assets (liabilities)	$ 11,341	$ 8,375