Income Taxes - Schedule of Income Taxes (Parenthetical) (Detail) - USD ($) $ in Thousands	Sep. 30, 2020	Sep. 30, 2019	Oct. 01, 2018	Sep. 30, 2018
Income Tax Disclosure [Line Items]
Deferred income taxes	$ 7,315	$ 6,176		$ 6,304
Income tax receivable	$ (2,391)	$ (558)		$ (1,152)
Adoption of ASC Topic 606 [Member]
Income Tax Disclosure [Line Items]
Deferred income taxes			$ 5,089
Income tax receivable			(762)
Impact of Adoption [Member] | Adoption of ASC Topic 606 [Member]
Income Tax Disclosure [Line Items]
Deferred income taxes			(1,215)
Income tax receivable			$ 390