Net Loss Per Share - Antidilutive Securities Excluded from Computation of Diluted Net Loss per Common Share of Common Stock Equivalents (Detail) - shares shares in Thousands	12 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Mar. 31, 2017
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of diluted net loss per common share (in shares)	5,199	5,324	6,666
Common stock reserved for issuance in connection with acquisition
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of diluted net loss per common share (in shares)	0	0	43
ESPP shares
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of diluted net loss per common share (in shares)	29	30	38
Restricted stock units
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of diluted net loss per common share (in shares)	2,419	2,079	1,978
Options to purchase common stock
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of diluted net loss per common share (in shares)	2,751	3,215	4,607