Supplementary Balance Sheet Information - Valuation Allowance for Deferred Tax Assets Activity (Details) - Valuation Allowance of Deferred Tax Assets - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2019
Movement in Valuation Allowances and Reserves [Roll Forward]
Valuation Allowances and Reserves, Balance, Beginning Balance	$ 10,623	$ 12,843	$ 14,613
Charged to Provisions	(3,247)	(2,514)	(1,834)
Charged to Other Accounts	1,216	294	64
Valuation Allowances and Reserves, Balance, Ending Balance	$ 8,592	$ 10,623	$ 12,843