Income Taxes (Components of Benefit from Income Taxes) (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Income Tax Disclosure [Abstract]
Domestic	$ (3,086)	$ (339)	$ (8,805)	$ (76,130)
Foreign	10,872	9,898	16,619	8,713
Provision (benefit) for income taxes	$ 7,786	$ 9,559	$ 7,814	$ (67,417)
Effective tax rate	45.70%	(85.60%)	55.70%	32.40%