Stock Based Compensation - Summary of Stock Incentive Plans (Details) - USD ($)		12 Months Ended
	May 12, 2015	Dec. 31, 2018	Dec. 31, 2017
Shares Available for Grant
Beginning balance (in shares)		513,385
Ending balance (in shares)		162,892	513,385
Stock Options Outstanding
Beginning balance (in shares)		2,984,304
Ending balance (in shares)		2,944,148	2,984,304
RSUs Outstanding
Beginning balance (in shares)		392,923
Ending balance (in shares)		392,904	392,923
Options vested, exercisable and expected to vest
Options exercised (in shares)		0	0
Weighted average grant date fair value of stock options granted (in dollars per share)		$ 1.60	$ 1.95
Number of options vested (in shares)		881,314	687,634
Weighted average fair value of options vested on grant date		$ 2,055,576	$ 712,718
Stock-based compensation expense		$ 2,023,874	$ 814,613
Inducement options
Stock Options Outstanding
Options granted (in shares)		209,531
Ending balance (in shares)		208,865
Options vested, exercisable and expected to vest
Weighted average grant date fair value of stock options granted (in dollars per share)		$ 1.34
Stock-based compensation expense		$ 52,577
Common Stock
Options vested, exercisable and expected to vest
Share Price		$ 0.23
2013 Plan
Stock Based Compensation
Option shares outstanding		33,769
2014 Plan
Shares Available for Grant
Beginning balance (in shares)		3,619
Additional shares authorized (in shares)		2,877,766
Options granted (in shares)		(2,868,673)
Options cancelled (in shares)		150,180
Ending balance (in shares)		162,892	3,619
Stock Options Outstanding
Beginning balance (in shares)		229,575
Options granted (in shares)		2,868,673
Options cancelled (in shares)		(154,100)
Ending balance (in shares)		2,944,148	229,575
RSUs Outstanding
Beginning balance (in shares)		392,904
Ending balance (in shares)		392,904	392,904
Weighted Average Stock Option Exercise Price
Beginning balance (in dollars per share)		$ 28.05
Options granted (in dollars per share)		1.60
Options cancelled (in dollars per share)		4.57
Ending balance (in dollars per share)		$ 5.81	$ 28.05
Weighted Average Remaining Contractual Life (Years)
Weighted Average Remaining Contractual Life (Years)		9 years 2 months 27 days	8 years 3 months 22 days
Options vested, exercisable and expected to vest
Options vested and exercisable (in shares)		616,309
Options vested and exercisable (in dollars per share)		$ 10.86
Options vested and exercisable (in years)		8 years 10 months 24 days
Options vested and expected to vest (in shares)		2,849,994
Options vested and expected to vest (in dollars per share)		$ 6.02
Options vested and expected to vest (in years)		9 years 2 months 27 days
2014 Plan | Stock options
Stock Based Compensation
Increase in share reserve based on outstanding number of shares (as a percent)	2.00%