CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS (Parenthetical) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2018	Dec. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Allocated share-based compensation expense	$ 39.6	$ 24.0	$ 127.5	$ 70.0
Cost of sales
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Allocated share-based compensation expense	3.4	3.5	10.9	10.6
Research and development
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Allocated share-based compensation expense	19.4	10.9	53.2	31.8
Selling, general and administrative
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Allocated share-based compensation expense	16.6	9.6	46.1	27.6
Special (income) charges and other, net
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Allocated share-based compensation expense	$ 0.2	$ 0.0	$ 17.3	$ 0.0