Net Loss Per Share Attributable to Common Stockholders- Excluded From Calculation (Details) - shares	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
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)	5,764,705	14,158,537
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)	2,944,148	3,444,663
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)	2,427,653	4,820,025
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	5,893,849