Segment Information - Net Sales and Gross Profit (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2020	Dec. 31, 2019
Segment reporting information [Line Items]
Net Sales	$ 1,352.1	$ 1,287.4	$ 3,971.3	$ 3,947.8
Gross Profit	845.8	785.5	2,452.0	2,428.2
Semiconductor products
Segment reporting information [Line Items]
Net Sales	1,319.9	1,257.0	3,893.9	3,875.6
Gross Profit	813.6	755.1	2,374.6	2,356.0
Technology licensing
Segment reporting information [Line Items]
Net Sales	32.2	30.4	77.4	72.2
Gross Profit	$ 32.2	$ 30.4	$ 77.4	$ 72.2