Summary of Significant Accounting Policies - Computation of Earnings (Loss) per Common Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Basic loss per share computation:
Net loss	$ (8,724)	$ (4,802)
Weighted average common shares - basic and diluted	53,805,983	53,458,513
Basic and diluted loss per share (in dollars per share)	$ (0.16)	$ (0.09)