Income Taxes - Effective Income Tax Reconciliation (Details) - USD ($) $ in Thousands	12 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Mar. 31, 2017
Effective Income Tax Rate Reconciliation, Amount
Income tax benefit at Bermuda statutory rate	$ 0	$ 0	$ 0
Foreign rate differential	(31,252)	(14,802)	(7,592)
Valuation allowance	32,335	13,966	7,378
Tax reform	0	1,049	0
Other	(607)	0	140
Total income tax expense (benefit)	$ 476	$ 213	$ (74)
Effective Income Tax Rate Reconciliation, Percent
Income tax benefit at Bermuda statutory rate	0.00%	0.00%	0.00%
Foreign rate differential	11.44%	10.35%	9.09%
Valuation allowance	(11.83%)	(9.77%)	(8.83%)
Tax reform	0.00%	(0.73%)	0.00%
Other	0.22%	0.00%	(0.17%)
Total income tax expense (benefit)	(0.17%)	(0.15%)	0.09%