Goodwill and Intangible Assets - Amortization Expense Associated with Intangible Assets (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Mar. 31, 2021	Mar. 31, 2020
Finite-Lived Intangible Assets [Line Items]
Amortization expense of intangible assets	$ 945	$ 1,202	$ 1,882	$ 2,998
Completed Technology
Finite-Lived Intangible Assets [Line Items]
Amortization expense of intangible assets	323	463	645	1,038
Customer Contracts [Member]
Finite-Lived Intangible Assets [Line Items]
Amortization expense of intangible assets	578	658	1,149	1,798
Trade Names [Member]
Finite-Lived Intangible Assets [Line Items]
Amortization expense of intangible assets	0	38	0	75
Noncompete Agreements [Member]
Finite-Lived Intangible Assets [Line Items]
Amortization expense of intangible assets	$ 44	$ 43	$ 88	$ 87