Restructuring and Other Similar Charges - Restructuring Reserve Rollforward (Details) - USD ($) $ in Millions	12 Months Ended			108 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Mar. 31, 2018	Mar. 31, 2020
Restructuring Reserve [Roll Forward]
Accrued Restructuring Costs, Beginning of Period	$ 4.3	$ 2.6
Charges	15.5	12.1	$ 14.1	$ 110.8
Cash payments	(10.0)	(10.1)
Non-cash charges		(0.3)
Accrued Restructuring Costs, End of Period	9.8	4.3	2.6	9.8
Employee termination benefits
Restructuring Reserve [Roll Forward]
Accrued Restructuring Costs, Beginning of Period	2.4	2.3
Charges	13.3	7.1	5.2	78.5
Cash payments	(7.4)	(7.0)
Non-cash charges		0.0
Accrued Restructuring Costs, End of Period	8.3	2.4	2.3	8.3
Asset impairment charges
Restructuring Reserve [Roll Forward]
Accrued Restructuring Costs, Beginning of Period	0.0	0.0
Charges	0.0	0.3
Cash payments	0.0	0.0
Non-cash charges		(0.3)
Accrued Restructuring Costs, End of Period	0.0	0.0	0.0	0.0
Contract termination and other associated costs
Restructuring Reserve [Roll Forward]
Accrued Restructuring Costs, Beginning of Period	1.9	0.3
Charges	2.2	4.7	8.1	28.7
Cash payments	(2.6)	(3.1)
Non-cash charges		0.0
Accrued Restructuring Costs, End of Period	$ 1.5	$ 1.9	$ 0.3	$ 1.5