Goodwill and Intangible Assets - Amortization Expense Associated with Intangible Assets (Detail) - USD ($) $ in Thousands		3 Months Ended		9 Months Ended
		Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Finite-Lived Intangible Assets [Line Items]
Amortization expense of intangible assets	[1]	$ 1,448	$ 1,571	$ 4,453	$ 5,043
Completed Technology
Finite-Lived Intangible Assets [Line Items]
Amortization expense of intangible assets		452	628	1,440	1,949
Other Intangible Assets
Finite-Lived Intangible Assets [Line Items]
Amortization expense of intangible assets		$ 996	$ 943	$ 3,013	$ 3,094

[1] Cost of revenues and selling, general and administrative expenses exclude the amortization of intangible assets. See Note 4.