Net Sales (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Disaggregation of Revenue [Line Items]
Total net sales	$ 1,649.8	$ 1,309.5	$ 3,219.2	$ 2,619.2
Distributors
Disaggregation of Revenue [Line Items]
Total net sales	816.7	663.2	1,600.1	1,322.1
Direct customers
Disaggregation of Revenue [Line Items]
Total net sales	800.3	623.0	1,558.9	1,251.9
Licensees
Disaggregation of Revenue [Line Items]
Total net sales	32.8	23.3	60.2	45.2
Microcontrollers
Disaggregation of Revenue [Line Items]
Total net sales	894.0	703.1	1,796.5	1,419.5
Analog
Disaggregation of Revenue [Line Items]
Total net sales	490.9	361.7	923.0	731.9
Other
Disaggregation of Revenue [Line Items]
Total net sales	$ 264.9	$ 244.7	$ 499.7	$ 467.8