Summary of Significant Accounting Policies (Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share) (Details) - shares	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Antidilutive Securities Excluded from Computation of Earnings Per Share
Anti-dilutive shares not included in the calculation of diluted net loss per share	2,757,932	29,666,872
Preferred stock | Series A convertible preferred stock
Antidilutive Securities Excluded from Computation of Earnings Per Share
Anti-dilutive shares not included in the calculation of diluted net loss per share	0	1,705,138
Preferred stock | Series B convertible preferred stock
Antidilutive Securities Excluded from Computation of Earnings Per Share
Anti-dilutive shares not included in the calculation of diluted net loss per share	0	2,234,668
Preferred stock | Series C convertible preferred stock
Antidilutive Securities Excluded from Computation of Earnings Per Share
Anti-dilutive shares not included in the calculation of diluted net loss per share	0	2,453,018
Preferred stock | Series D convertible preferred stock
Antidilutive Securities Excluded from Computation of Earnings Per Share
Anti-dilutive shares not included in the calculation of diluted net loss per share	0	6,653,633
Preferred stock | Series E-1 convertible preferred stock
Antidilutive Securities Excluded from Computation of Earnings Per Share
Anti-dilutive shares not included in the calculation of diluted net loss per share	0	7,316,744
Preferred stock | Series E-2 convertible preferred stock
Antidilutive Securities Excluded from Computation of Earnings Per Share
Anti-dilutive shares not included in the calculation of diluted net loss per share	0	5,129,592
Warrants | Preferred stock warrants | Series C convertible preferred stock
Antidilutive Securities Excluded from Computation of Earnings Per Share
Anti-dilutive shares not included in the calculation of diluted net loss per share	0	78,781
Warrants | Preferred stock warrants | Series D convertible preferred stock
Antidilutive Securities Excluded from Computation of Earnings Per Share
Anti-dilutive shares not included in the calculation of diluted net loss per share	0	160,056
Warrants | Preferred stock warrants | Series E-1 convertible preferred stock
Antidilutive Securities Excluded from Computation of Earnings Per Share
Anti-dilutive shares not included in the calculation of diluted net loss per share	0	8,674
Warrants | Preferred stock warrants | Series E-2 convertible preferred stock
Antidilutive Securities Excluded from Computation of Earnings Per Share
Anti-dilutive shares not included in the calculation of diluted net loss per share	0	17,252
Warrants | Common stock warrants
Antidilutive Securities Excluded from Computation of Earnings Per Share
Anti-dilutive shares not included in the calculation of diluted net loss per share	93,080	85,181
Equity options
Antidilutive Securities Excluded from Computation of Earnings Per Share
Anti-dilutive shares not included in the calculation of diluted net loss per share	2,664,852	3,824,135