Organization and Summary of Significant Accounting Policies - Antidilutive Securities (Details) - shares	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Number of securities that are antidilutive	12,890,956	10,815,230	9,629,348
Outstanding stock options
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Number of securities that are antidilutive	4,053,605	3,955,548	2,351,237
Outstanding warrants
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Number of securities that are antidilutive	8,837,351	6,859,682	6,185,492
Convertible notes payable
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Number of securities that are antidilutive	0	0	1,065,891
Restricted stock
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Number of securities that are antidilutive	0	0	26,728