Stockholders' Equity - Options Outstanding (Details) - $ / shares	3 Months Ended	12 Months Ended
	Mar. 31, 2020	Dec. 31, 2019
Number of Shares
Balance at the beginning of the period (in shares)	7,568,304
Granted (in shares)	230,000
Forfeited/Cancelled (in shares)	(207,874)
Balance at the end of the period (in shares)	7,590,430	7,568,304
Vested or expected to vest at the end of the period (in shares)	7,590,430
Exercisable at the end of the period (in shares)	4,812,040
Weighted-Average Exercise Price
Balance at the beginning of the period (in dollars per share)	$ 3.40
Granted (in dollars per share)	0.80
Forfeited/Cancelled (in dollars per share)	(3.69)
Balance at the end of the period (in dollars per share)	3.32	$ 3.40
Vested or expected to vest at the end of the period (in dollars per share)	3.32
Exercisable at the end of the period (in dollars per share)	$ 4.23
Weighted Average Remaining Contractual Term
Options Outstanding at the end of the period	6 years 11 months 9 days	7 years 4 days
Vested or expected to vest at the end of the period	6 years 11 months 9 days
Exercisable at the end of the period	6 years 11 days