Net Sales (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2020	Dec. 31, 2019
Disaggregation of Revenue [Line Items]
Total net sales	$ 1,352.1	$ 1,287.4	$ 3,971.3	$ 3,947.8
Distributors
Disaggregation of Revenue [Line Items]
Total net sales	681.6	638.8	2,003.7	1,970.0
Direct customers
Disaggregation of Revenue [Line Items]
Total net sales	638.3	618.2	1,890.2	1,905.6
Licensees
Disaggregation of Revenue [Line Items]
Total net sales	32.2	30.4	77.4	72.2
Microcontrollers
Disaggregation of Revenue [Line Items]
Total net sales	726.3	685.8	2,145.8	2,091.8
Analog
Disaggregation of Revenue [Line Items]
Total net sales	372.8	363.3	1,104.7	1,143.6
FPGA
Disaggregation of Revenue [Line Items]
Total net sales	99.1	92.6	294.3	276.8
LMO
Disaggregation of Revenue [Line Items]
Total net sales	$ 153.9	$ 145.7	$ 426.5	$ 435.6