Income Taxes (Components of Benefit from Income Taxes) (Detail) - USD ($) $ in Thousands	3 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Domestic	$ 834	$ (80,665)
Foreign	152	1,696
Provision (benefit) for income taxes	$ 986	$ (78,969)
Effective tax rate	5.30%	250.70%