Quarterly Results (Unaudited) (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended								12 Months Ended
	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2020	Mar. 31, 2019	Mar. 31, 2018	Mar. 31, 2017	Mar. 31, 2015
Quarterly Financial Information Disclosure [Abstract]
Net sales	$ 1,326.4	$ 1,287.4	$ 1,337.8	$ 1,322.6	$ 1,329.8	$ 1,374.7	$ 1,432.5	$ 1,212.5	$ 5,274.2	$ 5,349.5	$ 3,980.8
Gross Profit	813.9	785.5	827.5	815.2	820.5	779.6	689.3	642.0	3,242.1	2,931.3	2,420.7
Operating income	160.7	131.2	183.6	171.6	284.6	194.7	102.7	132.3	647.1	714.3	936.3
Net income	$ 99.9	$ 311.1	$ 108.9	$ 50.7	$ 174.7	$ 49.2	$ 96.3	$ 35.7	$ 570.6	$ 355.9	$ 255.4
Diluted net income per common share (in dollars per share)	$ 0.39	$ 1.20	$ 0.43	$ 0.20	$ 0.70	$ 0.20	$ 0.38	$ 0.14	$ 2.23	$ 1.42	$ 1.03
Tax benefit related to intra-group transfers of certain intellectual property rights		$ 334.8							$ 334.8	$ 90.6	$ 0.0
Loss on settlement of debt	$ 3.4			$ 1.9	$ 8.3		$ 4.1		$ 5.4	$ 12.6	$ 16.0	$ 43.9	$ 50.6