Consolidated Statements of Stockholders' Equity (Deficit) - USD ($) $ in Thousands	Restricted Stock Units (RSUs) [Member] Preferred Stock [Member] Convertible Preferred Stock [Member]	Restricted Stock Units (RSUs) [Member] Common Stock [Member]	Preferred Stock [Member] Convertible Preferred Stock [Member]	Common Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]	Total
Balance (in shares) at Dec. 31, 2015			110,500,514	1,578,962
Balance at Dec. 31, 2015			$ 46,030	$ 2	$ 358	$ (49,832)	$ (3,442)
Exchange of convertible preferred stock warrants to common stock (in shares)				10,807
Exchange of convertible preferred stock warrants to common stock					25		25
Reclassification of convertible shareholder notes derivative liability					2,268		2,268
Conversion of convertible notes into common stock (in shares)				8,091,103
Conversion of convertible notes into common stock				$ 8	12,148		12,156
Conversion of preferred stock into common stock (in shares)			(110,500,514)	9,208,376
Conversion of preferred stock into common stock			$ (46,030)	$ 9	46,021
Issuance of common stock upon reverse merger (in shares)				19,228,595
Issuance of common stock upon reverse merger				$ 19	18,902		18,921
Exercise of stock options (in shares)				13,460
Exercise of stock options					22		22
Share-based compensation					942		942
Net loss						(10,310)	(10,310)
Balance (in shares) at Dec. 31, 2016				38,131,303
Balance at Dec. 31, 2016				$ 38	80,686	(60,142)	20,582
Exercise of stock options (in shares)				87,357
Exercise of stock options					144		144
Share-based compensation					2,707		2,707
Net loss						(12,308)	(12,308)
Balance (in shares) at Dec. 31, 2017				38,218,660
Balance at Dec. 31, 2017				$ 38	83,537	(72,450)	$ 11,125
Exercise of stock options (in shares)				2,140			2,488
Exercise of stock options				$ 0	4		$ 4
Share-based compensation					2,774		2,774
Net loss						(13,987)	(13,987)
Adjustments to opening balance for change in accounting principle at Dec. 31, 2017						76	76
Sale of common stock and warrants, net of issuance costs of $200				$ 5	3,795		3,800
Sale of common stock and warrants, net of issuance costs of $200 (in shares)				5,333,332
Restricted stock units vested and issued (in shares)		57,108
Balance (in shares) at Dec. 31, 2018				43,611,240
Balance at Dec. 31, 2018				$ 43	$ 90,110	$ (86,361)	$ 3,792