Stock-Based Compensation - Schedule of Stock Option Activity (Details) - Employee Stock Option	6 Months Ended
	Jun. 30, 2019 $ / shares shares
Number of Options
Number of options outstanding, balance beginning (in shares) | shares	4,352,391
Number of options issued (in shares) | shares	2,158,202
Number of options exercised (in shares) | shares	0
Number of options forfeited (in shares) | shares	(144,510)
Number of options expired (in shares) | shares	(112,646)
Number of options outstanding, balance ending (in shares) | shares	6,253,437
Number of options exercisable (in shares) | shares	3,583,374
Weighted Average Exercise Price
Shares outstanding exercise price, balance beginning (in dollars per share) | $ / shares	$ 4.61
Issued, exercise price (in dollars per share) | $ / shares	1.50
Exercised, exercise price (in dollars per share) | $ / shares	0
Forfeited, exercise price (in dollars per share) | $ / shares	3.80
Expired, exercise price (in dollars per share) | $ / shares	5.84
Shares outstanding exercise price, balance ending (in dollars per share) | $ / shares	3.53
Exercisable, exercise price (in dollars per share) | $ / shares	$ 4.65