Stockholders' Equity - Common Stock Warrants (Details) - $ / shares		1 Months Ended	3 Months Ended
	Jun. 19, 2018	Feb. 28, 2019	Mar. 31, 2019	Mar. 31, 2018
February 2019 common stock warrants
Convertible Preferred Stock
Number of warrants issued		2,000,000
Exercise price of warrants (in dollars per share)		$ 6.25
Warrants term		5 years
Warrants outstanding			1,999,500
Weighted average remaining contractual life			4 years 10 months 10 days
June 2018 common stock warrants
Convertible Preferred Stock
Number of warrants issued	4,200,000
Exercise price of warrants (in dollars per share)	$ 12.00
Warrants term	5 years
Weighted average remaining contractual life			4 years 2 months 23 days
Common Stock
Convertible Preferred Stock
Number of shares issued			353,746	539,026
Oppenheimer & Co. Inc | Common Stock | June 2018 common stock warrants
Convertible Preferred Stock
Number of shares issued	4,200,000
Share price (in dollars per share)	$ 0.001