Net Sales (Details) - USD ($) $ in Millions	12 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Mar. 31, 2019
Disaggregation of Revenue [Line Items]
Total net sales	$ 5,438.4	$ 5,274.2	$ 5,349.5
Revenue, payment terms	30 days
Distributors
Disaggregation of Revenue [Line Items]
Total net sales	$ 2,737.4	2,626.9	2,719.1
Direct customers
Disaggregation of Revenue [Line Items]
Total net sales	2,598.1	2,550.4	2,498.0
Licensees
Disaggregation of Revenue [Line Items]
Total net sales	102.9	96.9	132.4
Microcontrollers
Disaggregation of Revenue [Line Items]
Total net sales	2,961.0	2,817.9	2,921.9
Analog
Disaggregation of Revenue [Line Items]
Total net sales	1,519.8	1,511.1	1,530.7
Other
Disaggregation of Revenue [Line Items]
Total net sales	$ 957.6	$ 945.2	$ 896.9