Common Stock and Stockholders' Equity - Additional Information (Detail) $ / shares in Units, $ in Thousands	1 Months Ended			3 Months Ended		6 Months Ended
	Dec. 31, 2014 shares	May 31, 2014 USD ($) director $ / shares shares	Aug. 31, 2013 USD ($) director $ / shares shares	Sep. 30, 2016 USD ($) $ / shares shares	Sep. 30, 2015 USD ($) shares	Sep. 30, 2016 USD ($) $ / shares shares	Sep. 30, 2015 USD ($) shares	Mar. 31, 2016 $ / shares shares
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) | $ / shares				$ 0.001		$ 0.001		$ 0.001
Stock-based compensation expense | $				$ 8,263	$ 5,588	$ 15,601	$ 10,247
Fair value granted restricted stock awards shares of common stock (in shares)						1,095,000
Grant date fair value of restricted stock awards (in usd per share) | $ / shares						$ 27.41
Stock options granted (in shares)						300,000
Unrecognized stock-based compensation cost related to outstanding unvested stock awards | $				$ 24,700		$ 24,700
Stock-based compensation cost expected to be recognized over weighted-average period				2 years 1 month 22 days
Expected to vest unrecognized stock-based compensation cost related to outstanding unvested stock options | $				$ 58,400		58,400
Director
Class of Stock [Line Items]
Number of directors | director		2
Nonemployees
Class of Stock [Line Items]
Stock-based compensation expense | $				$ 200	$ 300	$ 400	$ 500
Stock options granted (in shares)				1,728	7,306	16,812	11,607
Restricted Stock Awards
Class of Stock [Line Items]
Stock-based compensation expense | $					$ 100		$ 200
Common stock vesting period			4 years
Restricted Stock Awards | Director
Class of Stock [Line Items]
Stock-based compensation expense | $				$ 100		$ 200
Number of directors | director			2
Fair value granted restricted stock awards shares of common stock (in shares)		40,000	100,000
Common stock vesting period		4 years
Fair value of the restricted stock awards, value | $		$ 700	$ 900
Grant date fair value of restricted stock awards (in usd per share) | $ / shares		$ 16.93	$ 9.37
Restricted stock awards, vested (in shares)				107,499		107,499
Unvested Stock Options
Class of Stock [Line Items]
Stock based compensation cost is expected to be recognized over a weighted-average period				3 years 8 days
Employee Stock Purchase Plan
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)				118,658	0	118,658	0
Stock-based compensation expense | $				$ 400	$ 200	$ 900	$ 200
Shares available for issuance (in shares)				1,741,172		1,741,172
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)				8,138,093		8,138,093
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%