Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Statement Of Financial Position [Abstract]
Allowances for doubtful accounts receivable	$ 143	$ 135
Preferred stock, par value	$ 0.001	$ 0.001
Preferred stock, shares authorized	5,000,000	5,000,000
Preferred stock, shares issued	5,500	5,500
Preferred stock, shares outstanding	1,335	1,345
Common stock, par value	$ 0.001	$ 0.001
Common stock, shares authorized	100,000,000	100,000,000
Common stock, shares issued	32,041,685	28,241,129
Common stock, shares outstanding	32,041,685	28,241,129