Equity Incentive Plans - Additional Information (Detail) - USD ($)				1 Months Ended		12 Months Ended
	Jan. 01, 2016	Jan. 01, 2015	Jun. 18, 2014	Jan. 31, 2016	Jun. 30, 2015	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Aug. 31, 2011
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period						4 years
Common stock reserved						1,454,549
Increase in shares reserved for issuance, maximum shares to be issued up on exercise of stock options			1,153,279
Weighted-average grant-date estimated fair value of options granted						$ 12.91	$ 18.53	$ 2.68
Estimated fair value of common stock						$ 18.12
Fair value of options vested during period						$ 2,400,000	$ 500,000	$ 200,000
Shares available for future grant						1,644,420	1,265,282	3,914	96,841
Stock-based compensation charge							$ 800,000
Gross proceeds from issuance of common stock					$ 77,800,000
Proceeds from issuance of common stock, net of issuance costs					$ 74,300,000	$ 74,323,000	$ 61,241,000
Common stock sold and issued					7,242,992
Purchase price of common shares					$ 10.70
Warrants issued to purchase common stock					2,172,899
Purchase price for warrants					$ 0.125					$ 0.09
Warrants exercise price per share					$ 13.91
Warrants expiration term					5 years
Warrants description						The warrants are exercisable for an exercise price of $13.91 per share at any time prior to the earlier of (i) 5 years from the date of issuance or (ii) certain changes in control of the Company.
Maximum warrants ownership percentage by each holder of warrants					9.99%
Number of warrants exercised						0
Expected dividend yield						$ 0
Options Issued and Outstanding Number of Shares, Options granted						379,709	188,888	99,552
Issuance of common stock for services (Shares)						13,285	10,000
Issuance of common stock for services, amount						$ 194,000	$ 208,000
Subsequent Event [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Increase in shares reserved for issuance, maximum shares to be issued up on exercise of stock options	1,038,595
Proceeds from issuance of common stock, net of issuance costs				$ 80,400,000
Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based award accelerated vesting number of shares							58,969
Options to Purchase Common Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized stock based compensation expense						$ 5,600,000
Unrecognized stock based compensation expense, weighted-average remaining recognition period						2 years 7 months 6 days
Non Employee Stock Option [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted-average grant-date estimated fair value of options granted						$ 18.58	$ 20.77	$ 3.43
Stock-based compensation charge						$ 200,000	$ 100,000
Options Issued and Outstanding Number of Shares, Options granted						5,000	10,000	3,333
2014 Equity Incentive Award Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock reserved						1,419,328
Increase in shares reserved for issuance, maximum shares to be issued up on exercise of stock options						10,683,053
Possible increase in shares reserved for issuance as percentage of outstanding stock						4.00%
2008 Stock Incentive Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock reserved						35,221
2014 Employee Stock Purchase Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock reserved						202,762
Increase in shares reserved for issuance, maximum shares to be issued up on exercise of stock options		185,892				2,230,374
Possible increase in shares reserved for issuance as percentage of outstanding stock						1.00%
Employee stock purchase plan initial offering commenced period						Sep. 01, 2014
Employee stock purchase plan initial offering ending period						Feb. 27, 2015
Number of shares authorized for issuance						388,654
Shares available for future grant						347,074
Number of shares sold under the plan						41,580	0
Weighted-average purchase price						$ 13.25
Proceeds from issuance of shares						$ 600,000
Unrecognized stock based compensation expense						$ 100,000
Unrecognized stock based compensation expense, weighted-average remaining recognition period						2 months 12 days