Property, Plant and Equipment (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Jun. 30, 2018	Mar. 31, 2018
Property, Plant and Equipment [Line Items]
Gross property, plant and equipment	$ 1,276.3	$ 1,302.2
Less: accumulated depreciation	(789.4)	(797.9)
Net property, plant and equipment	486.9	504.3
Land [Member]
Property, Plant and Equipment [Line Items]
Gross property, plant and equipment	21.5	22.6
Buildings and Improvements [Member]
Property, Plant and Equipment [Line Items]
Gross property, plant and equipment	$ 287.4	$ 295.6
Property, plant and equipment, depreciable lives	10 years	40 years
Machinery and Equipment [Member]
Property, Plant and Equipment [Line Items]
Gross property, plant and equipment	$ 823.9	$ 840.8
Property, plant and equipment, depreciable lives	3 years	12 years
Office Equipment [Member]
Property, Plant and Equipment [Line Items]
Gross property, plant and equipment	$ 89.8	$ 93.0
Property, plant and equipment, depreciable lives	3 years	10 years
Construction in Progress [Member]
Property, Plant and Equipment [Line Items]
Gross property, plant and equipment	$ 53.7	$ 50.2