Net Sales (Details) - USD ($) $ in Millions	3 Months Ended
	Jun. 30, 2019	Jun. 30, 2018
Disaggregation of Revenue [Line Items]
Net sales	$ 1,322.6	$ 1,212.5
Distributors
Disaggregation of Revenue [Line Items]
Net sales	665.1	645.7
Direct customers
Disaggregation of Revenue [Line Items]
Net sales	638.9	540.1
Licensees
Disaggregation of Revenue [Line Items]
Net sales	18.6	26.7
Microcontrollers
Disaggregation of Revenue [Line Items]
Net sales	708.3	722.5
Analog, interface, mixed signal and timing products
Disaggregation of Revenue [Line Items]
Net sales	386.4	331.9
Field-programmable gate array products
Disaggregation of Revenue [Line Items]
Net sales	91.0	37.8
Licensing, memory and other
Disaggregation of Revenue [Line Items]
Net sales	$ 136.9	$ 120.3