Other Comprehensive Income (Loss) - Reclassifications out of Accumulated Other Comprehensive Income (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2017
Affected Line in the Consolidated Statement of Operations:
Net revenue	$ 485.8	$ 446.6	$ 464.6	$ 410.3	$ 474.7	$ 446.0	$ 452.2	$ 397.2	$ 1,807.3	$ 1,770.1	$ 1,590.2
Cost of Goods and Services Sold									1,184.3	1,128.0	999.4
Operating expenses									(379.7)	(378.9)	(343.5)
Other (expense) income, net									(6.7)	0.2	(4.6)
Tax expense									(50.5)	(65.3)	(59.9)
Total reclassifications for the period, net of tax									5.7	1.7	3.1
Pension and Postretirement
Affected Line in the Consolidated Statement of Operations:
Total reclassifications for the period, net of tax									1.2	3.0	3.4
Net Unrealized Gain (Loss) on Derivative Instruments
Affected Line in the Consolidated Statement of Operations:
Total reclassifications for the period, net of tax									4.5	(1.3)	(0.3)
Reclassification out of Accumulated Other Comprehensive Income
Affected Line in the Consolidated Statement of Operations:
Net revenue									0.2	0.5	(0.1)
Cost of Goods and Services Sold									0.8	0.1	0.5
Other (expense) income, net									8.2	1.5	5.1
Income before income taxes									7.6	1.9	4.5
Tax expense									(1.9)	(0.2)	(1.4)
Total reclassifications for the period, net of tax									5.7	1.7	3.1
Reclassification out of Accumulated Other Comprehensive Income | Net Loss Recognized
Affected Line in the Consolidated Statement of Operations:
Net revenue									0.0	0.0	0.0
Cost of Goods and Services Sold									0.0	0.0	0.0
Other (expense) income, net									1.7	3.6	4.6
Income before income taxes									1.7	3.6	4.6
Reclassification out of Accumulated Other Comprehensive Income | Prior Service Costs Recognized
Affected Line in the Consolidated Statement of Operations:
Net revenue									0.0	0.0	0.0
Cost of Goods and Services Sold									0.0	0.0	0.0
Other (expense) income, net									0.0	0.2	0.4
Income before income taxes									0.0	0.2	0.4
Reclassification out of Accumulated Other Comprehensive Income | Net Unrealized Gain (Loss) on Derivative Instruments
Affected Line in the Consolidated Statement of Operations:
Net revenue									0.2	0.5	(0.1)
Cost of Goods and Services Sold									0.8	0.1	0.5
Other (expense) income, net									6.5	(2.3)	0.1
Income before income taxes									$ 5.9	$ (1.9)	$ (0.5)