Stockholders' Equity - Schedule of Warrants Outstanding (Details) - Warrants to purchase common stock - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2019	Dec. 31, 2018
Number of Shares
Outstanding at beginning of period (in shares)	353,610
Exercised (in shares)	0
Outstanding at end of period (in shares)	353,610	353,610
Exercisable (in shares)	353,610
Weighted- average Exercise Price
Outstanding at beginning of period (in dollars per share)	$ 9.78
Exercised (in dollars per share)	0.00
Outstanding at end of period (in dollars per share)	9.78	$ 9.78
Exercisable (in dollars per share)	$ 9.78
Weighted- average Remaining Contractual Term (years)
Outstanding	4 years 4 months 10 days	4 years 4 months 10 days
Exercisable	4 years 4 months 10 days
Aggregate Intrinsic Value
Outstanding	$ 1,181	$ 1,181
Exercisable	$ 1,181