Income Taxes - Income Tax (Benefit) Provision from Continuing Operations (Details) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Mar. 31, 2019
Pretax (loss) income:
U.S.	$ (301.7)	$ (485.2)	$ (593.4)
Foreign	641.2	635.6	797.9
Income before income taxes	339.5	150.4	204.5
Current expense (benefit):
U.S. Federal	54.8	21.1	(98.0)
State	2.0	1.0	(5.3)
Foreign	72.2	48.0	14.1
Total current expense (benefit)	129.0	70.1	(89.2)
Deferred expense (benefit):
U.S. Federal	(215.4)	(127.8)	11.9
State	(22.9)	(13.2)	0.6
Foreign	99.4	(349.3)	(74.7)
Total deferred benefit	(138.9)	(490.3)	(62.2)
Total income tax benefit	(9.9)	(420.2)	(151.4)
Effective Income Tax Rate Reconciliation, Amount [Abstract]
Computed expected income tax provision	71.3	31.5	43.0
State income taxes, net of federal benefit	(3.8)	(5.4)	(8.7)
Foreign income taxed at lower than the federal rate	(45.7)	(78.8)	(94.0)
Impact of the TCJA - one-time transition tax, net of foreign tax credits	0.0	0.0	13.1
GILTI and foreign-derived intangible income, net of credits	101.8	54.7	95.4
Business realignment of intellectual property rights	(63.8)	(334.8)	(90.6)
Net increases related to current year tax positions	49.8	20.1	9.0
Net decreases related to prior year tax positions	(4.4)	(28.5)	(75.1)
Share-based compensation	(12.3)	(11.1)	(13.3)
Research and development tax credits	(48.4)	(40.8)	(27.5)
Intercompany prepaid tax asset amortization	0.0	0.0	5.2
Foreign exchange	(6.5)	(0.9)	4.6
Convertible debt settlement	(48.1)	0.0	0.0
Subpart-F income	6.4	4.1	10.7
Other	7.1	(1.7)	(13.3)
Change in valuation allowance	(13.3)	(28.6)	(9.9)
Total income tax benefit	$ (9.9)	$ (420.2)	$ (151.4)
Increase of basic net income per share due to release of prior year tax positions (in dollars per share)	$ 0.02	$ 0.12	$ 0.32
Increase of diluted net income per share due to release of prior year tax positions (in dollars per share)	$ 0.02	$ 0.11	$ 0.30