Retirement Plans - Narrative (Details) - USD ($) $ in Millions	9 Months Ended	12 Months Ended
	Jun. 30, 2022	Jun. 30, 2023	Sep. 30, 2021	Sep. 30, 2020
Retirement Benefits [Abstract]
Employer matching contributions (as a percent)	50.00%
Maximum employee's pretax contribution that can be matched (as a percent)	6.00%
Employer matching contributions	$ 4.7		$ 1.9	$ 2.0
Liability, Defined Benefit Plan	7.0	$ 8.7
Defined Benefit Plan, Accumulated Other Comprehensive Income (Loss), Gain (Loss), before Tax	0.8	0.1
Defined Benefit Plan, Plan Assets, Amount	4.6	4.8
Defined Benefit Plan, Benefit Obligation	11.6	13.6
Defined Contribution Plan, Cost	$ 2.0	$ 2.7	$ 5.1