Retirement Benefits (Schedule of Amount of Expense Associated with Defined Contribution Plans) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Compensation And Retirement Disclosure [Abstract]
Company costs	$ 8,647	$ 8,005	$ 25,180	$ 25,619