Net Loss Per Share Attributable to Common Stockholders- Excluded From Calculation (Details) - shares	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Outstanding common stock equivalents have been excluded from diluted net loss per common share
Outstanding common stock equivalents have been excluded from diluted net loss per common share (in shares)	42,381,970	5,831,680
Options issued and outstanding
Outstanding common stock equivalents have been excluded from diluted net loss per common share
Outstanding common stock equivalents have been excluded from diluted net loss per common share (in shares)	2,843,754	1,043,070
Inducement options
Outstanding common stock equivalents have been excluded from diluted net loss per common share
Outstanding common stock equivalents have been excluded from diluted net loss per common share (in shares)	208,865
Warrants to purchase common stock
Outstanding common stock equivalents have been excluded from diluted net loss per common share
Outstanding common stock equivalents have been excluded from diluted net loss per common share (in shares)	5,027,495	321,335
Restricted stock units
Outstanding common stock equivalents have been excluded from diluted net loss per common share
Outstanding common stock equivalents have been excluded from diluted net loss per common share (in shares)	392,904	392,923
Preferred Convertible Stock
Outstanding common stock equivalents have been excluded from diluted net loss per common share
Outstanding common stock equivalents have been excluded from diluted net loss per common share (in shares)	33,149,556	3,314,956
Convertible notes
Outstanding common stock equivalents have been excluded from diluted net loss per common share
Outstanding common stock equivalents have been excluded from diluted net loss per common share (in shares)	759,396	759,396