Acquisitions and Divestitures (Ultrapure Acquisition) (Details) - USD ($) $ in Thousands			12 Months Ended
	Apr. 01, 2021	Dec. 17, 2020	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2019
Business Acquisition [Line Items]
Cash paid to acquire assets			$ 21,037	$ 13,108	$ 2,873
Goodwill			407,376	$ 397,205	$ 392,890
Ultrapure
Business Acquisition [Line Items]
Cash paid to acquire assets		$ 8,743
Business Combination, Provisional Information, Initial Accounting Incomplete, Adjustment, Consideration Transferred	$ 290
Net assets acquired		9,033
Business Acquisition, Transaction Costs			$ 230
Current assets		2,366
Property, plant, and equipment		963
Goodwill		2,836
Intangible assets		3,751
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Financial Assets		21
Total assets acquired		9,937
Other liabilities assumed		$ (904)