Income Taxes - Additional Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018
Income Taxes [Line Items]
Foreign pretax earnings	$ 62,100	$ 42,200	$ 36,000
Current foreign tax expense related to foreign tax withholdings	7,500	6,400	6,500
Unrecognized tax benefits	10,897	$ 7,994	$ 5,834	$ 6,113
Unrecognized tax benefits that would impact the effective tax rate if recognized	10,400
Unrecognized tax benefits, accrued interest	$ 400
Effective income tax rate	21.00%
Unremitted earnings of foreign subsidiaries	$ 141,500
California Franchise Tax Board | Research Tax Credit Carryforward
Income Taxes [Line Items]
Excess state research credit	17,100
Valuation allowance	17,100
U.S. Federal
Income Taxes [Line Items]
Net operating loss carryforwards	6,700
Foreign NOL carryforwards
Income Taxes [Line Items]
Net operating loss carryforwards	29,200
Foreign NOL carryforwards | China
Income Taxes [Line Items]
Net operating loss carryforwards	4,900
Foreign NOL carryforwards | GERMANY
Income Taxes [Line Items]
Net operating loss carryforwards	$ 18,100