Stockholders' Equity (Deficit) - Summary of Stock Option Transactions (Detail) - $ / shares	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Options granted	955,713	926,384
Weighted Average Remaining Contractual Term
Options vested at end of period	7 years 5 months 19 days	7 years 5 months 16 days
Options vested and expected to vest at end of period	8 years 9 months	8 years 8 months 1 day
Stock Options [Member]
Shares Available for Grant
Options Available, Beginning balance	606,061	124,824
Options Available, Authorized	6 years 1 month 6 days
Options Available, Additional shares authorized	270,764
Options exercised	0
Options Available, Granted	(955,713)	(926,384)
Options Available, Forfeited	85,037	93,979
Options Available, Ending balance	6,149	606,061
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Beginning balance	1,072,011	239,606
Options granted	955,713	926,384
Options exercised	(83,848)
Options canceled/forfeited	(85,037)	(93,979)
Ending balance	1,858,839	1,072,011
Weighted-Average Exercise Price per Share
Beginning balance (in dollars per share)	$ 6.34	$ 3.36
Options granted (in dollars per share)	3.08	7.15
Options exercised (in dollars per share)	3.50
Options canceled/forfeited (in dollars per share)	5.03	6.75
Ending balance (in dollars per share)	$ 4.82	$ 6.34
Weighted Average Remaining Contractual Term
Options outstanding at end of period	8 years 9 months	8 years 8 months 1 day
Options vested at end of period (shares)	922,927	578,889
Options vested at end of period (in dollars per share)	$ 5.06	$ 5.58
Options vested and expected to vest at end of period (shares)	1,858,839	1,072,011
Options vested and expected to vest at end of period (in dollars per share)	$ 4.82	$ 6.34
Stock Options [Member] | 2014 Plan [Member]
Shares Available for Grant
Options Available, Additional shares authorized		1,437,165
Stock Options [Member] | Closed 2010 Plan [Member]
Shares Available for Grant
Options Available, Expired		(123,523)
Minimum [Member] | Stock Options [Member]
Shares Available for Grant
Options Available, Authorized		5 years 9 months 18 days