Income Taxes - Deferred Taxes (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Mar. 31, 2017
Deferred tax assets:
Research tax credits	$ 2,948	$ 163
Net operating loss	16,045	6,019
Share-based compensation	2,380	1,382
Other	169	300
Subtotal	21,542	7,864
Valuation allowance	(21,367)	(7,401)
Deferred tax liabilities:
Depreciation	(175)	(255)
Total deferred tax assets	$ 0	$ 208