Stock Incentive Plans - Summary of Activity of Stock Incentive and Equity Plans (Detail) - $ / shares	3 Months Ended	9 Months Ended
	Sep. 30, 2015	Sep. 30, 2015
Shares available for grant
Shares available for grant, Beginning balance		1,772,529
Shares available for grant, Granted		(563,839)
Shares available for grant, Exercised		0
Shares available for grant, Cancelled/forfeited		307,410
Shares available for grant, Ending balance	1,516,100	1,516,100
Number of options outstanding
Number of options outstanding, Beginning balance		2,238,286
Number of options outstanding, Granted		458,600
Number of options outstanding, Exercised		(5,692)
Shares available for grant, Cancelled/forfeited		(272,208)
Number of options outstanding, Ending balance	2,418,986	2,418,986
Weighted - average option exercise price
Weighted - average option exercise price, Beginning balance		$ 10.31
Weighted - average option exercise price, Granted		1.85
Weighted - average option exercise price, Exercised		0.78
Shares available for grant, Cancelled/forfeited		11.02
Weighted - average option exercise price, Ending balance	$ 8.64	$ 8.64
Number of restricted stock and board shares issued
Number of restricted stock shares issued, Beginning balance		140,653
Number of restricted stock shares issued, Granted		60,802
Number of restricted stock shares issued, Exercised	0	0
Shares available for grant, Cancelled/forfeited		0
Number of restricted stock shares issued, Ending balance	201,455	201,455
Restricted Stock Units [Member]
Number of restricted stock units outstanding
Number of restricted stock units outstanding, Beginning balance		134,731
Number of restricted stock units outstanding, Granted		44,437
Number of restricted stock units outstanding, Exercised		0
Shares available for grant, Cancelled/forfeited		(46,452)
Number of restricted stock units outstanding, Ending balance	132,716	132,716