Income Taxes - Effective Income Tax Reconciliation (Details) - USD ($) $ in Thousands	12 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Mar. 31, 2019
Effective Income Tax Rate Reconciliation, Amount
Income tax expense at Bermuda statutory rate	$ 0	$ 0	$ 0
Foreign rate differential	(37,622)	(40,056)	(31,252)
Impact of changes in enacted income tax rates	0	(27,150)	0
Currency remeasurement effects on Swiss deferred tax assets	(13,742)	0	0
Officer’s non-deductible share-based compensation	9,590	0	0
Share-based compensation deferral adjustment	(4,364)	4,089	0
R&D tax credits (net of uncertain tax positions)	(3,771)	(1,208)	0
Valuation allowance	50,333	65,193	32,335
Other	(88)	(107)	(607)
Total income tax expense	$ 336	$ 761	$ 476
Effective Income Tax Rate Reconciliation, Percent
Income tax expense at Bermuda statutory rate	0.00%	0.00%	0.00%
Foreign rate differential	14.77%	13.90%	11.44%
Impact of changes in enacted income tax rates	0.00%	9.42%	0.00%
Currency remeasurement effects on Swiss deferred tax assets	5.39%	0.00%	0.00%
Officer’s non-deductible share-based compensation	(3.76%)	0.00%	0.00%
R&D tax credits (net of uncertain tax positions)	1.48%	0.42%	0.00%
Share-based compensation deferral adjustment	1.71%	(1.42%)	0.00%
Valuation allowance	(19.75%)	(22.62%)	(11.83%)
Other	0.03%	0.04%	0.22%
Total income tax expense	(0.13%)	(0.26%)	(0.17%)