Income Taxes - Schedule of Deferred Tax Assets and Liabilities (Detail) - USD ($) $ in Thousands	Mar. 31, 2019	Mar. 31, 2018
Deferred tax assets:
Accrued expenses	$ 3,768	$ 2,558
Depreciation and amortization	2,461	3,585
Net operating loss carryforwards	126,125	98,338
Stock based compensation	6,754	5,248
Research and development credits	15,960	12,351
Other	0	0
Gross deferred tax assets	155,068	122,080
Valuation allowance	(126,793)	(117,353)
Total deferred tax assets	28,275	4,727
Deferred tax liabilities:
Prepaids	(2,889)	(2,647)
Intangibles	(2,349)
Capitalized research and development	(2,165)	(1,942)
Deferred contract acquisition costs	(12,515)	0
Convertible debt	7,570	0
Total deferred tax liabilities	(27,488)	(4,589)
Total net deferred tax assets/(liabilities)	$ 787	$ 138