Summary of Significant Accounting Policies - Summary of Outstanding Potentially Dilutive Securities Excluded from Calculation of Diluted Net Loss Per Share (Detail)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Total excluded securities	815,008	730,750
Warrants to purchase common stock [Member]
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Total excluded securities	118,881	106,000
Common stock options [Member]
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Total excluded securities	683,500	624,750
Employee stock purchase plan [Member]
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Total excluded securities	12,627