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Income Taxes - Narrative (Details) - USD ($) $ in Thousands	12 Months Ended
Income Taxes - Narrative (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2017	Nov. 30, 2018
Income Tax Contingency [Line Items]
Blended tax rate		24.50%
Effective tax rate	20.00%	7.00%	44.00%
Tax expense		$ 500
Undistributed earnings of foreign subsidiaries	$ 19,400
Tax credit carryforwards	2,000
Valuation allowance related to deferred tax assets	8,231	$ 9,597
Decrease in unrecognized tax benefits due to expiration of certain federal statutes of limitations	900
Refund related to U.S. federal carryback claim				$ 6,600
R&D Tax Credit
Income Tax Contingency [Line Items]
Retroactive tax benefit			$ 900
International
Income Tax Contingency [Line Items]
Operating loss carryforwards	$ 2,900