CONDENSED CONSOLIDATED STATEMENTS OF INCOME (PARENTHETICAL) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Allocated share based compensation expense	$ 45.3	$ 42.6	$ 86.0	$ 87.9
Cost of sales
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Allocated share based compensation expense	5.2	3.9	10.1	7.5
Research and development
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Allocated share based compensation expense	22.3	19.7	41.8	33.8
Selling, general and administrative
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Allocated share based compensation expense	17.8	17.8	34.1	29.5
Special charges and other, net
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Allocated share based compensation expense	$ 0.0	$ 1.2	$ 0.0	$ 17.1