Income Taxes - Deferred Taxes (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Apr. 01, 2018	Mar. 31, 2018
Deferred tax assets:
Research tax credits	$ 7,224		$ 2,948
Net operating loss	38,194		16,045
Share-based compensation	6,106		2,380
Intangibles	38,673		0
Other	2,539		169
Subtotal	92,736		21,542
Valuation allowance	(92,330)		(21,367)
Deferred tax liabilities:
Depreciation	(406)		(175)
Total deferred tax assets	$ 0		$ 0
Accounting Standards Update 2016-16
Deferred tax assets:
Intangibles		$ 38,700
Valuation allowance		$ (38,700)