Income Taxes - Narrative (Details) - USD ($)	12 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Mar. 31, 2019	Mar. 31, 2018
Income Tax Disclosure [Abstract]
Effective income tax rate	(0.13%)	(0.26%)	(0.17%)
Operating Loss Carryforwards [Line Items]
Effective income tax rate	(0.13%)	(0.26%)	(0.17%)
Deferred tax assets valuation allowance	$ 207,858,000	$ 157,525,000
Change in unrecognized tax benefits	1,200,000	3,200,000
Unrecognized tax benefit	4,404,000	3,177,000	$ 0	$ 0
Significant change in unrecognized tax benefits over the next twelve months	0
Unrecognized tax benefit, accrual for interest and penalties	0
Recognized interest and/or penalties	0	$ 0	$ 0
Deferred employer payroll taxes	1,800,000
Deferred employer payroll taxes, current	900,000
Deferred employer payroll taxes, noncurrent	900,000
Switzerland
Operating Loss Carryforwards [Line Items]
Net operating losses	876,000,000.0
Ireland
Operating Loss Carryforwards [Line Items]
Net operating losses	200,000
United Kingdom
Operating Loss Carryforwards [Line Items]
Net operating losses	31,000,000.0
United States | Research and Development Credit Carryforward
Operating Loss Carryforwards [Line Items]
Credit carryforwards	7,700,000
California | Research and Development Credit Carryforward
Operating Loss Carryforwards [Line Items]
Credit carryforwards	$ 2,300,000