Stockholders' Equity - Warrants (Details) - $ / shares		3 Months Ended	12 Months Ended
	Apr. 28, 2020	Mar. 31, 2020	Dec. 31, 2019
Number of Warrants
Balance of warrants outstanding at the end of the period (in shares)		10,516,377	10,589,482
Granted (in shares)		931,967
Exercised (in shares)		(1,005,072)
Balance of warrants outstanding at the beginning of the period (in shares)		10,589,482
Weighted Average Exercise Price Per Share
Weighted average exercise price of warrants at the beginning of the period (in USD per share)		$ 4.08
Granted (in USD per share)		0.95
Exercised (in USD per share)		1.56
Weighted average exercise price of warrants at the end of the period (in USD per share)		$ 4.04	$ 4.08
Term
Weighted-Average Remaining Contractual Term		3 years 7 months	3 years 8 months 21 days
Pre-Funded Warrants
Number of Warrants
Exercised (in shares)		(131,967)
Subsequent Event | Pre-Funded Warrants
Number of Warrants
Exercised (in shares)	(131,967)