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	6 Months Ended
	Sep. 30, 2017	Sep. 30, 2016
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of diluted net loss per common share	5,858	7,776
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	41	36
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	43	90
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	2,180	2,159
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	3,594	5,491