Special Charges and Other, Net - Special Charges (Details) - USD ($) $ in Millions		12 Months Ended
		Mar. 31, 2019	Mar. 31, 2018	Mar. 31, 2017
Other Nonrecurring (Income) Expense [Abstract]
Employee separation costs		$ 65.3	$ 1.2	$ 39.1
Gain on sale of assets		0.0	(4.4)	0.0
Impairment charges		3.6	0.0	12.6
Contract exit costs		(4.7)	0.7	44.1
Other		(0.3)	0.0	2.8
Legal contingencies		(30.2)	0.0	0.0
Non-restructuring contract exit costs and other		0.0	20.0	0.0
Total	[1]	$ 33.7	$ 17.5	$ 98.6

[1] (1) Includes share-based compensation expense as follows: Cost of sales$14.9 $13.8 $18.7Research and development$72.0 $42.5 $46.8Selling, general and administrative$62.3 $36.9 $62.6Special charges and other, net$17.2 $— $—