Special Charges and Other, Net - Narrative (Details) - USD ($) $ in Millions	12 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Mar. 31, 2018
Restructuring Cost and Reserve [Line Items]
Costs associated with restructuring	$ 18.0
Asset impairment charges	2.5
Remaining associated costs with restructuring activities (less than)	10.0
Net charges related to legal settlements	15.7	$ (30.2)	$ 0.0
Non-restructuring contract exit costs and other	0.0	0.0	20.0
Employee separation costs	6.0	65.3	1.2
Gain on sale of assets	1.5	0.0	4.4
Contract exit costs (income)	13.4	(4.7)	0.7
Restructuring reserve	24.3	47.8	47.2
Atmel Corporation
Restructuring Cost and Reserve [Line Items]
Employee separation costs			1.2
Micrel Incorporated
Restructuring Cost and Reserve [Line Items]
Proceeds from sale of property, plant, and equipment			10.0
Gain on sale of assets			4.4
Contract Termination
Restructuring Cost and Reserve [Line Items]
Restructuring cost incurred	8.2
Non-restructuring contract exit costs and other			$ 19.5
Termination period			5 years
Supply agreement term			10 years
Contract Termination | Semiconductor Products
Restructuring Cost and Reserve [Line Items]
Restructuring and related cost, costs incurred to date	53.5
Other Relocation Costs
Restructuring Cost and Reserve [Line Items]
Restructuring cost incurred	6.6
Restructuring reserve	12.0	15.7	$ 19.1
Employee Separation
Restructuring Cost and Reserve [Line Items]
Restructuring reserve	6.1	12.9	0.8
Employee Separation | Semiconductor Products
Restructuring Cost and Reserve [Line Items]
Employee separation costs	6.0	$ 65.3	$ 1.2
Restructuring and related cost, costs incurred to date	$ 111.6