Income Taxes - Narrative (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended	12 Months Ended
	Dec. 31, 2019	Mar. 31, 2020	Mar. 31, 2019	Mar. 31, 2018	Mar. 31, 2017
Income Tax Disclosure [Abstract]
Income tax holiday, aggregate dollar amount		$ 11.4		$ 6.2
Income tax holiday expense, aggregate dollar amount			$ 0.1
Income tax holiday, benefits per share, basic (in dollars per share)		$ 0.05	$ 0	$ 0.03
Income tax holiday, benefits per share, diluted (in dollars per share)		$ 0.04	$ 0	$ 0.02
Tax benefit related to intra-group transfers of certain intellectual property rights	$ 334.8	$ 334.8	$ 90.6	$ 0.0
Reduction in effective tax rate related to intra-group transfers of certain intellectual property rights		222.90%
Deferred tax asset representing the book and tax basis difference on transferred assets		$ 78.0
Deferred tax liability representing the book and tax basis difference on transferred assets		259.9
Operating Loss Carryforwards [Line Items]
Capital loss carryforward		9.4	9.6
Refundable foreign tax credits		4.1
Tax credits, research activity		104.1
Tax credits, prior year		9.2
Tax credits, foreign jurisdictions		45.1
Unrecognized tax benefits, income tax penalties accrued		74.6	88.1
Unrecognized tax benefits, income tax penalties and interest expense		13.5	37.5	5.4
Unrecognized Tax Benefits		757.3	763.4	$ 436.0	$ 398.5
Unrecognized tax benefits that would impact effective tax rate		654.0	$ 664.4
Unrecognized tax benefits, potential decrease		10.0
Foreign Tax Authority and Federal and State Jurisdiction
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards		74.8
State and Local Jurisdiction
Operating Loss Carryforwards [Line Items]
Tax credit carryforward, amount		168.2
Foreign Tax Authority | Foreign Withholding Tax Credit
Operating Loss Carryforwards [Line Items]
Tax credit carryforward, amount		$ 20.4