CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY - USD ($) $ in Thousands	Common Stock [Member]	Additional Paid-in Capital [Member]	Accumulated Deficit [Member]	Accumulated Other Comprehensive Loss [Member]	Total
Balance at Dec. 31, 2015	$ 5	$ 144,778	$ (129,669)	$ (19)	$ 15,095
Balance (in shares) at Dec. 31, 2015	53,198,835
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock issued for cash, net	$ 1	19,195			19,196
Stock issued for cash, net (in shares)	4,760,594
Stock-based compensation		5,398			5,398
Exercise of options		20			20
Exercise of options (in shares)	50,357
Stock issued for vested RSUs (in shares)	135,102
Comprehensive income:
Net loss			(28,569)		(28,569)
Other comprehensive income (loss), net of tax				7	7
Comprehensive loss					(28,562)
Balance at Dec. 31, 2016	$ 6	169,391	(158,238)	(12)	11,147
Balance (in shares) at Dec. 31, 2016	58,144,888
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock issued for cash, net		3,677			3,677
Stock issued for cash, net (in shares)	730,444
Stock-based compensation		3,986			3,986
Exercise of options		22			22
Exercise of options (in shares)	12,500
Stock issued for vested RSUs (in shares)	164,146
Comprehensive income:
Net loss			(17,278)		(17,278)
Other comprehensive income (loss), net of tax				(1)	(1)
Comprehensive loss					(17,279)
Balance at Dec. 31, 2017	$ 6	177,076	(175,516)	(13)	1,553
Balance (in shares) at Dec. 31, 2017	59,051,978
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cumulative effect of accounting change | ASU Topic 606 [Member]			2,500		2,500
Stock issued for cash, net	$ 1	27,051			27,052
Stock issued for cash, net (in shares)	7,510,555
Stock-based compensation		4,055			4,055
Exercise of options		135			135
Exercise of options (in shares)	117,229
Stock issued for vested RSUs (in shares)	200,085
Comprehensive income:
Net loss			(25,406)		(25,406)
Other comprehensive income (loss), net of tax				(1)	(1)
Comprehensive loss					(25,407)
Balance at Dec. 31, 2018	$ 7	$ 208,317	$ (198,422)	$ (14)	$ 9,888
Balance (in shares) at Dec. 31, 2018	66,879,847