Income Taxes - Narrative (Details) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Mar. 31, 2019	Mar. 31, 2018
Income Tax Disclosure [Abstract]
Income tax holiday, aggregate dollar amount	$ 11.1	$ 11.4
Income tax holiday, benefits per share, basic (in dollars per share)	$ 0.04	$ 0.05
Income tax holiday, benefits per share, diluted (in dollars per share)	$ 0.04	$ 0.04
Tax benefit related to intra-group transfers of certain intellectual property rights	$ 63.8	$ 334.8	$ 90.6
Reduction in effective tax rate related to intra-group transfers of certain intellectual property rights	18.80%
Deferred tax asset representing the book and tax basis difference on transferred assets	$ 155.5
Deferred tax liability representing the book and tax basis difference on transferred assets	90.3
Operating Loss Carryforwards [Line Items]
Capital loss carryforward	6.3	9.4
Refundable foreign tax credits	1.9
Tax credits, research activity	85.0
Tax credits, prior year	4.7
Tax credits, foreign jurisdictions	56.6
Unrecognized tax benefits, income tax penalties accrued	83.9	74.6
Unrecognized tax benefits, income tax penalties and interest expense	9.3	13.5	37.5
Unrecognized Tax Benefits	826.3	757.3	$ 763.4	$ 436.0
Unrecognized tax benefits that would impact effective tax rate	720.5	$ 654.0
Unrecognized tax benefits, potential decrease	10.0
Cumulative income tax expense impact of Altera decision	23.3
Foreign Tax Authority and Federal and State Jurisdiction
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards	68.0
State and Local Jurisdiction
Operating Loss Carryforwards [Line Items]
Tax credit carryforward, amount	163.0
Foreign Tax Authority | Foreign Withholding Tax Credit
Operating Loss Carryforwards [Line Items]
Tax credit carryforward, amount	$ 19.9