Income Taxes - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2012
Income Taxes [Line Items]
Foreign pretax earnings	$ 45,200	$ 43,300	$ 24,300
Current foreign tax expense related to foreign tax withholdings	$ 5,300	$ 7,700	$ 4,800
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	$ 52,800
Unrecognized tax benefits	4,634	$ 4,554	$ 9,009	$ 7,501
Unrecognized tax benefits that would impact the effective tax rate if recognized	4,000
Unrecognized tax benefits, accrued interest	200
U.S. federal
Income Taxes [Line Items]
Net operating loss carryforwards	$ 23,900
Net operating loss carryforwards expiration dates	2024
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	$ 34,200
Foreign NOL carryforwards | China
Income Taxes [Line Items]
Net operating loss carryforwards	22,000
CA state research credit
Income Taxes [Line Items]
Excess state research credit	5,700
Valuation allowance	$ 5,700