Segment Information (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2018	Dec. 31, 2017
Segment reporting information [Line Items]
Net Sales	$ 1,374.7	$ 994.2	$ 4,019.7	$ 2,978.5
Gross Profit	779.6	607.1	2,110.9	1,805.6
Semiconductor products
Segment reporting information [Line Items]
Net Sales	1,331.3	966.7	3,911.4	2,900.2
Gross Profit	736.2	579.6	2,002.6	1,727.3
Technology licensing
Segment reporting information [Line Items]
Net Sales	43.4	27.5	108.3	78.3
Gross Profit	$ 43.4	$ 27.5	$ 108.3	$ 78.3