Goodwill and Intangible Assets - Amortization Expense Associated with Intangible Assets (Detail) - USD ($) $ in Thousands	3 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Finite-Lived Intangible Assets [Line Items]
Amortization expense of intangible assets	$ 937	$ 1,796
Completed Technology
Finite-Lived Intangible Assets [Line Items]
Amortization expense of intangible assets	322	575
Customer Contracts [Member]
Finite-Lived Intangible Assets [Line Items]
Amortization expense of intangible assets	571	1,140
Trade Names [Member]
Finite-Lived Intangible Assets [Line Items]
Amortization expense of intangible assets	0	37
Noncompete Agreements [Member]
Finite-Lived Intangible Assets [Line Items]
Amortization expense of intangible assets	$ 44	$ 44