Common Stock and Stockholders' Equity - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands	1 Months Ended	3 Months Ended		6 Months Ended
	Dec. 31, 2014	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Mar. 31, 2017
Class of Stock [Line Items]
Common stock, shares authorized (in shares)		100,000,000		100,000,000		100,000,000
Common stock, par value (in usd per share)		$ 0.001		$ 0.001		$ 0.001
Stock-based compensation expense		$ 10,222	$ 8,263	$ 19,845	$ 15,601
Unrecognized stock-based compensation cost related to outstanding unvested stock awards		19,000		$ 19,000
Stock-based compensation cost expected to be recognized over weighted-average period				2 years 24 days
Expected to vest unrecognized stock-based compensation cost related to outstanding unvested stock options		$ 70,500		$ 70,500
Unvested Stock Options
Class of Stock [Line Items]
Stock based compensation cost is expected to be recognized over a weighted-average period				2 years 9 months 3 days
ESPP shares
Class of Stock [Line Items]
Shares reserved for issuance under plan (in shares)		1,000,000		1,000,000
Additional shares available for issuance under the plan (in shares)	500,000
Percentage of common stock shares increased under the plan	1.00%
Common stock purchased under Employee Stock Purchase Plan (in shares)		101,493	118,658	101,493	118,658
Stock-based compensation expense		$ 600	$ 400	$ 1,000	$ 900
Shares available for issuance (in shares)		2,046,251		2,046,251
2008 Equity Incentive Plan
Class of Stock [Line Items]
Shares available for issuance (in shares)		0		0
2014 Equity Incentive Plan
Class of Stock [Line Items]
Shares reserved for issuance under plan (in shares)	5,000,000
Shares available for issuance (in shares)		9,889,781		9,889,781
Shares available for grant under plan (in shares)	5,184,878
Increase in shares available under plan, percentage of outstanding common stock shares	5.00%