Accumulated Other Comprehensive Income (Loss) - Schedule of Reclassifications Out of Accumulated Other Comprehensive Income (Loss) on Condensed Consolidated Statements of Income (Details) - USD ($) $ in Millions	3 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Prior Service Costs
Reclassification out of Accumulated Other Comprehensive Income [Line Items]
Total before tax	$ 0.2	$ 0.2
Actuarial (Gains) Losses
Reclassification out of Accumulated Other Comprehensive Income [Line Items]
Total before tax	0.3	1.3
Employee Pension and Postretirement Benefits, Net of Tax
Reclassification out of Accumulated Other Comprehensive Income [Line Items]
Total before tax	0.5	1.5
Tax benefit	(0.1)	(0.3)
Net of tax	$ 0.4	$ 1.2