Income Taxes - Components of Net Deferred Tax Liabilities (Detail) - USD ($) $ in Thousands	Sep. 30, 2020	Sep. 30, 2019
Deferred tax assets -
Valuation reserves and non-deductible expenses	$ 4,848	$ 1,253
Stock compensation expense not deductible	1,804	2,158
Net operating loss and tax credit carryforwards	10,164	494
Basis difference in equity-method investee	302	302
Inventory basis differences	382	289
Other	207	125
Subtotal	17,707	4,621
Less valuation allowance	(302)	(408)
Deferred tax assets	17,405	4,213
Deferred tax liabilities -
Fixed asset basis differences and depreciation	(4,269)	(2,205)
Intangible asset basis differences and amortization	(9,293)	(4,374)
Deferred tax liabilities	(13,562)	(6,579)
Net deferred tax assets (liabilities)	$ 3,843	$ 2,366