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Debt - Additional Information (Detail) - USD ($)		12 Months Ended
Debt - Additional Information (Detail) - USD ($)	Dec. 19, 2014	Mar. 31, 2018	Mar. 31, 2017	Mar. 31, 2016	Mar. 17, 2017	Mar. 16, 2017
Debt Instrument [Line Items]
Amortization of debt discount (less than 0.1 million)		$ 19,000	$ 156,000	$ 359,000
Term debt \| Hercules Technology Growth Capital \| FIrst warrants
Debt Instrument [Line Items]
Number of shares received from warrants received to purchase common stock (in shares)	13,927
Fair value of warrants issued	$ 400,000
Term debt \| Hercules Technology Growth Capital \| Second warrants
Debt Instrument [Line Items]
Number of shares received from warrants received to purchase common stock (in shares)	25,641
Fair value of warrants issued	$ 200,000
Term debt \| Hercules Technology Growth Capital \| Hercules warrants
Debt Instrument [Line Items]
Number of shares received from warrants received to purchase common stock (in shares)	58,823
Exercise price (in dollars per share)	$ 7.85
Term loan C \| Term debt \| Hercules Technology Growth Capital
Debt Instrument [Line Items]
Debt, face amount	$ 1,500,000.0
Net proceeds from debt	$ 1,400,000
Interest rate on loan					11.25%	11.00%
Term loan
Debt Instrument [Line Items]
Interest expense, debt (less than 0.1 million)		100,000	400,000	1,000,000
Amortization of debt discount (less than 0.1 million)		$ 100,000	$ 200,000	$ 400,000