Income Taxes - Additional Information (Detail) - USD ($)	12 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Operating Loss Carryforwards [Line Items]
Unrecognized tax benefits	$ 0
Increase (decrease) in valuation allowance	39,000	$ (3,200,000)
Federal net operating loss carryforwards	170,300,000
State net operating loss carryforwards	$ 49,200,000
Federal net operating loss carryforwards (“NOLs”) expiring year	2028
State net operating loss carryforwards (“NOLs”) expiring year	2028
Federal research tax credit carryforwards expiration period	2028
Federal statutory tax rate	21.00%	35.00%
Valuation allowance for deferred tax	$ 2,700,000
Accrued expense regarding interest or penalties	0
Federal [Member]
Operating Loss Carryforwards [Line Items]
Operating loss carry forwards	24,100,000
Research tax credit carryforwards	$ 4,000,000
Federal [Member] | Maximum [Member]
Operating Loss Carryforwards [Line Items]
Percentage of future taxable income to be offset	80.00%
State [Member]
Operating Loss Carryforwards [Line Items]
Research tax credit carryforwards	$ 3,600,000