Segment Information - Net Sales and Gross Profit (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Segment reporting information [Line Items]
Net Sales	$ 1,649.8	$ 1,309.5	$ 3,219.2	$ 2,619.2
Gross Profit	1,068.3	807.9	2,075.9	1,606.2
Semiconductor products
Segment reporting information [Line Items]
Net Sales	1,617.0	1,286.2	3,159.0	2,574.0
Gross Profit	1,035.5	784.6	2,015.7	1,561.0
Technology licensing
Segment reporting information [Line Items]
Net Sales	32.8	23.3	60.2	45.2
Gross Profit	$ 32.8	$ 23.3	$ 60.2	$ 45.2