Income Taxes - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2013
Income Taxes [Line Items]
Foreign pretax earnings	$ 33,000	$ 45,200	$ 43,300
Current foreign tax expense related to foreign tax withholdings	6,500	5,300	$ 7,700
Foreign tax credit carryforward	$ 14,590	$ 0
Foreign tax credit carry forward year	10 years
U.S. federal statutory income tax rate	35.00%	35.00%	35.00%
Excess amount for financial reporting over tax basis of investments in foreign subsidiaries	$ 45,300
Unrecognized tax benefits	6,799	$ 4,634	$ 4,554	$ 9,009
Unrecognized tax benefits that would impact the effective tax rate if recognized	6,000
Unrecognized tax benefits, accrued interest	300
California Franchise Tax Board | Research Tax Credit Carryforward
Income Taxes [Line Items]
Excess state research credit	6,100
Valuation allowance	6,100
U.S. Federal
Income Taxes [Line Items]
Net operating loss carryforwards	$ 20,200
Net operating loss carryforwards expiration dates	2020
State
Income Taxes [Line Items]
Net operating loss carryforwards	$ 300
Net operating loss carryforwards expiration dates	2021
Foreign NOL carryforwards
Income Taxes [Line Items]
Net operating loss carryforwards	$ 34,700
Foreign NOL carryforwards | China
Income Taxes [Line Items]
Net operating loss carryforwards	$ 25,500