Other Comprehensive Income (Loss) - Schedule of reclassifications (Details) - USD ($) $ in Millions	3 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Affected Line in the Consolidated Statement of Operations:
Net revenue	$ 566.9	$ 410.3
Cost of goods sold	(395.1)	(263.3)
Operating expenses	(157.4)	(90.7)
Other income, net	1.9	0.5
Tax expense	12.4	(14.5)
Total reclassifications for the period, net of tax	1.5	0.2
Amortization of Pension and Postretirement
Affected Line in the Consolidated Statement of Operations:
Total reclassifications for the period, net of tax	1.1	0.2
Derivative Instruments
Affected Line in the Consolidated Statement of Operations:
Total reclassifications for the period, net of tax	0.4	0.0
Reclassifications out of accumulated other comprehensive income (loss)
Affected Line in the Consolidated Statement of Operations:
Net revenue	0.1	0.1
Cost of goods sold	(0.2)	(0.1)
Other income, net	2.1	0.3
Total before tax	2.0	0.3
Tax expense	(0.5)	(0.1)
Total reclassifications for the period, net of tax	1.5	0.2
Reclassifications out of accumulated other comprehensive income (loss) | Net Loss Recognized
Affected Line in the Consolidated Statement of Operations:
Net revenue	0.0	0.0
Cost of goods sold	0.0	0.0
Other income, net	1.6	0.3
Total before tax	1.6	0.3
Reclassifications out of accumulated other comprehensive income (loss) | Prior Service Costs Recognized
Affected Line in the Consolidated Statement of Operations:
Net revenue	0.0	0.0
Cost of goods sold	0.0	0.0
Other income, net	0.0	0.0
Total before tax	0.0	0.0
Reclassifications out of accumulated other comprehensive income (loss) | Derivative Instruments
Affected Line in the Consolidated Statement of Operations:
Net revenue	0.1	0.1
Cost of goods sold	(0.2)	(0.1)
Other income, net	0.5	0.0
Total before tax	$ 0.4	$ 0.0