Goodwill and Intangible Assets - Amortization Expense Associated with Intangible Assets (Detail) - USD ($) $ in Thousands		3 Months Ended		9 Months Ended
		Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Finite-Lived Intangible Assets [Line Items]
Amortization expense of intangible assets	[1]	$ 1,571	$ 3,365	$ 5,043	$ 9,997
Cost of revenues
Finite-Lived Intangible Assets [Line Items]
Amortization expense of intangible assets		628	1,723	1,949	5,096
Selling, general and administrative expenses
Finite-Lived Intangible Assets [Line Items]
Amortization expense of intangible assets		$ 943	$ 1,642	$ 3,094	$ 4,901

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