Special Charges (Details) - USD ($) $ in Millions	12 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Mar. 31, 2016
Other Nonrecurring (Income) Expense [Abstract]
Employee separation costs	$ 1.2	$ 39.1	$ 9.6
Gain on sale of assets	(4.4)	0.0	0.0
Impairment charges	0.0	12.6	0.0
Contract exit costs	0.7	44.1	0.7
Other	0.0	2.8	0.9
Legal settlement costs	0.0	0.0	4.3
Insurance settlement	0.0	0.0	(11.5)
Non-restructuring contract exit costs and other	20.0	0.0	0.0
Total	$ 17.5	$ 98.6	$ 4.0