Stockholders' Equity - Stock-based Compensation Expense and Valuation Information - Additional Information (Detail)	12 Months Ended
	Mar. 31, 2019 USD ($)
Class Of Stock [Line Items]
Total unrecognized compensation cost related to unvested stock option grants	$ 7,439,000
Employee Stock Purchase Plan [Member]
Class Of Stock [Line Items]
Total unrecognized compensation cost related, weighted average period	5 months
Unrecognized stock-based compensation expense	$ 10,000
Stock options [Member]
Class Of Stock [Line Items]
Total unrecognized compensation cost related, weighted average period	2 years 8 months 26 days
Restricted stock units (RSUs) [Member]
Class Of Stock [Line Items]
Total unrecognized compensation cost related, weighted average period	2 years 5 months 26 days
Unrecognized stock-based compensation expense	$ 3,234,000
Performance-Based Restricted Stock Units [Member]
Class Of Stock [Line Items]
Total unrecognized compensation cost related, weighted average period	4 years 25 days
Unrecognized stock-based compensation expense	$ 136,000