Stockholders' Equity - Stock-based Compensation Expense and Valuation Information - Additional Information (Detail)	9 Months Ended
	Dec. 31, 2017 USD ($)
Class Of Stock [Line Items]
Total unrecognized compensation cost related to unvested stock option grants	$ 6,710,000
Employee Stock Purchase Plan [Member]
Class Of Stock [Line Items]
Total unrecognized compensation cost related, weighted average period	2 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 6 months 15 days
Restricted stock units (RSUs) [Member]
Class Of Stock [Line Items]
Total unrecognized compensation cost related, weighted average period	2 years 11 months 24 days
Unrecognized stock-based compensation expense	$ 4,768,000
Performance-Based Restricted Stock Units [Member]
Class Of Stock [Line Items]
Total unrecognized compensation cost related, weighted average period	2 years 3 months
Unrecognized stock-based compensation expense	$ 317,000
Restricted stock [Member]
Class Of Stock [Line Items]
Unrecognized stock-based compensation expense	$ 0