Summary of Significant Accounting Policies - Antidilutive Securities (Details) - shares	6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016
Net Loss Per Share
Antidilutive securities excluded from the calculation of basic and diluted loss per share (in shares)	9,433,438	11,113,067
Stock Option
Net Loss Per Share
Antidilutive securities excluded from the calculation of basic and diluted loss per share (in shares)	3,589,147	6,137,495
Warrants [Member]
Net Loss Per Share
Antidilutive securities excluded from the calculation of basic and diluted loss per share (in shares)	4,328,877	4,515,947
Restricted Stock Units (RSUs)
Net Loss Per Share
Antidilutive securities excluded from the calculation of basic and diluted loss per share (in shares)	1,452,289	396,500
Series A Convertible Preferred Stock
Net Loss Per Share
Antidilutive securities excluded from the calculation of basic and diluted loss per share (in shares)	63,125	63,125