Income Taxes- Narrative (Details) - USD ($) $ in Thousands	12 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Operating Loss Carryforwards [Line Items]
Effective income tax rate	(0.61%)	(0.10%)
Deferred tax asset	$ 188,861	$ 171,004
Valuation allowance on deferred tax assets	187,762	171,004
Income tax receivable	1,707	1,726
United States
Operating Loss Carryforwards [Line Items]
Net operating losses	102
Switzerland
Operating Loss Carryforwards [Line Items]
Net operating losses	1,210,000
United Kingdom
Operating Loss Carryforwards [Line Items]
Net operating losses	11,400
Ireland
Operating Loss Carryforwards [Line Items]
Net operating losses	13
Accounting Standards Update 2016-16
Operating Loss Carryforwards [Line Items]
Deferred tax asset		3,800
Valuation allowance on deferred tax assets		$ 3,800
Research and Development Tax Credit
Operating Loss Carryforwards [Line Items]
Tax credit carryforward	$ 10,800