Share-Based Compensation Plans - Share-Based Compensation Expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2019
Share-based Compensation, Allocation and Classification in Financial Statements [Abstract]
Tax benefit	$ (3,755)	$ (3,162)	$ (3,767)
Total share-based compensation expense, net of tax	15,923	13,234	14,460
Cost of sales
Share-based Compensation, Allocation and Classification in Financial Statements [Abstract]
Share-based compensation expense	2,970	2,863	2,727
Research, development and technical
Share-based Compensation, Allocation and Classification in Financial Statements [Abstract]
Share-based compensation expense	1,739	2,090	2,150
Selling, general and administrative
Share-based Compensation, Allocation and Classification in Financial Statements [Abstract]
Share-based compensation expense	$ 14,969	$ 11,443	$ 13,350