Special Charges and Other, Net - Income Statement Disclosure (Details) - USD ($) $ in Millions		3 Months Ended		6 Months Ended
		Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Other Nonrecurring (Income) Expense [Abstract]
Employee separation costs		$ 12.1	$ 0.3	$ 57.2	$ 1.4
Gain on sale of assets		0.0	0.0	0.0	(4.4)
Impairment charges		1.5	0.0	3.5	0.1
Contract exit costs		4.0	19.6	(3.0)	20.2
Other		0.6	0.0	0.6	(0.2)
Special charges and other, net	[1]	$ 18.2	$ 19.9	$ 58.3	$ 17.1

[1] (1) Includes share-based compensation expense as follows: Cost of sales$3.9 $3.7 $7.5 $7.1Research and development$19.7 $10.6 $33.8 $20.9Selling, general and administrative$17.8 $9.3 $29.5 $18.0Special charges and other, net$1.2 $— $17.1 $—