Income Taxes - Loss Before Income Taxes and Related Tax Benefit (Details) - USD ($) $ in Thousands	12 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Mar. 31, 2017
Loss before income taxes:
Bermuda	$ (14,357)	$ (6,513)	$ (50,845)
Total loss before income taxes	(273,075)	(143,042)	(83,514)
Current taxes:
Bermuda	0	0	0
Total current tax expense	476	5	134
Deferred taxes:
Bermuda	0	0	0
Total deferred tax expense (benefit)	0	208	(208)
Total income tax expense (benefit)	476	213	(74)
United States
Loss before income taxes:
Foreign	(11,246)	(7,229)	(2,924)
Current taxes:
Foreign	473	13	125
Deferred taxes:
Foreign	0	208	(208)
Switzerland
Loss before income taxes:
Foreign	(247,445)	(129,261)	(29,745)
Current taxes:
Foreign	0	0	0
Deferred taxes:
Foreign	0	0	0
Other
Loss before income taxes:
Foreign	(27)	(39)	0
Current taxes:
Foreign	3	(8)	9
Deferred taxes:
Foreign	$ 0	$ 0	$ 0