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, 2019	Dec. 31, 2018
Prior Service Costs
Reclassification out of Accumulated Other Comprehensive Income [Line Items]
Total before tax	$ 0.2
Actuarial (Gains) Losses
Reclassification out of Accumulated Other Comprehensive Income [Line Items]
Total before tax	0.7	$ (0.1)
Employee Pension and Postretirement Benefits, Net of Tax
Reclassification out of Accumulated Other Comprehensive Income [Line Items]
Total before tax	0.9	(0.1)
Tax provision (benefit)	(0.2)	$ 0.1
Net of tax	$ 0.7