Employee Benefit Plans - Change in Obligation (Details) - USD ($) $ in Millions	12 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Mar. 31, 2018
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Projected benefit obligation at the beginning of the year	$ 72.7	$ 61.0
Additions due to acquisition of Microsemi	0.0	9.8
Service costs	1.7	1.5	$ 2.2
Interest costs	0.9	1.1	1.0
Actuarial losses	(2.6)	6.0
Benefits paid	(1.5)	(0.9)
Foreign currency exchange rate changes	(1.2)	(5.8)
Projected benefit obligation at the end of the year	70.0	72.7	$ 61.0
Accumulated benefit obligation at the end of the year	$ 65.1	$ 66.7
Weighted average assumptions
Discount rate	1.48%	1.41%
Rate of compensation increase	2.77%	2.79%