Supplementary Balance Sheet Information - Product Warranty and Retrofit Activity on Gross Basis (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2019
Movement in Standard and Extended Product Warranty Accrual, Increase (Decrease) [Roll Forward]
Beginning Balance	$ 2,211	$ 2,314	$ 2,561
Accruals for warranties	2,300	2,779	2,014
Costs incurred	(2,181)	(2,882)	(2,261)
Ending Balance	$ 2,330	$ 2,211	$ 2,314