Net Sales (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2020	Mar. 31, 2019	Mar. 31, 2018
Disaggregation of Revenue [Line Items]
Total net sales	$ 1,326.4	$ 1,287.4	$ 1,337.8	$ 1,322.6	$ 1,329.8	$ 1,374.7	$ 1,432.5	$ 1,212.5	$ 5,274.2	$ 5,349.5	$ 3,980.8
Payment terms									30 days
Distributors
Disaggregation of Revenue [Line Items]
Total net sales									$ 2,626.9	2,719.1
Direct customers
Disaggregation of Revenue [Line Items]
Total net sales									2,550.4	2,498.0
Licensees
Disaggregation of Revenue [Line Items]
Total net sales									96.9	132.4
Microcontrollers
Disaggregation of Revenue [Line Items]
Total net sales									2,817.9	2,921.9
Analog, interface, mixed signal and timing products
Disaggregation of Revenue [Line Items]
Total net sales									1,511.1	1,530.7
Field-programmable gate array products
Disaggregation of Revenue [Line Items]
Total net sales									373.5	303.8
Licensing, memory and other
Disaggregation of Revenue [Line Items]
Total net sales									$ 571.7	$ 593.1