Summary of Significant Accounting Policies - Schedule of Common Share Equivalents Included from Computation of Net Loss Per Share (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Earnings Per Share [Abstract]
Net loss available to stockholders of the company	$ (3,496)	$ (2,970)	$ (9,491)	$ (11,006)
Interest accumulated on preferred shares and on preferred shares contingently issuable for little or no cash				(328)
Net loss attributable to shareholders of preferred shares and to shareholders of preferred shares contingently issuable for little or no cash				2,666
Net loss used in the calculation of basic and diluted loss per share	$ (3,496)	$ (2,970)	$ (9,491)	$ (8,668)
Net loss per share, basic and diluted	$ (0.37)	$ (0.43)	$ (1.07)	$ (2.25)
Weighted-average number of common shares	9,420,039	6,943,058	8,864,895	3,845,258