Condensed Consolidated Statement of Changes in Stockholders' Equity - USD ($) $ in Thousands	Total	Common Stock	Treasury Stock	Additional Paid-In Capital	Accumulated Other Comprehensive Loss	Accumulated Deficit
Balance at beginning of period at Dec. 31, 2017	$ 83,139	$ 5	$ (8,443)	$ 288,277	$ (232)	$ (196,468)
Balance at beginning of period (in shares) at Dec. 31, 2017		55,136,038	3,845,496
Increase (Decrease) in Stockholders' Equity
Exercise of stock options awards	1,018			1,018
Exercise of stock options awards (in shares)		314,711
Stock-based compensation expense	856			856
Common stock issued for settlement of restricted stock units net of shares withheld to satisfy income tax withholding obligations	(912)			(912)
Common stock issued for settlement of restricted stock units net of shares withheld to satisfy income tax withholding obligations (in shares)		433,317
Common stock issuance in connection with employee stock purchase plan	240			240
Common stock issuance in connection with employee stock purchase plan (in shares)		84,415
Net loss	(6,101)					(6,101)
Foreign currency translation adjustment	(70)				(70)
Balance at end of period at Mar. 31, 2018	78,170	$ 5	$ (8,443)	289,479	(302)	(202,569)
Balance at end of period (in shares) at Mar. 31, 2018		55,968,481	3,845,496
Balance at beginning of period at Dec. 31, 2017	83,139	$ 5	$ (8,443)	288,277	(232)	(196,468)
Balance at beginning of period (in shares) at Dec. 31, 2017		55,136,038	3,845,496
Increase (Decrease) in Stockholders' Equity
Net loss	(10,801)
Foreign currency translation adjustment	(417)
Balance at end of period at Sep. 30, 2018	75,809	$ 5	$ (8,443)	292,166	(649)	(207,269)
Balance at end of period (in shares) at Sep. 30, 2018		56,813,104	3,845,496
Balance at beginning of period at Mar. 31, 2018	78,170	$ 5	$ (8,443)	289,479	(302)	(202,569)
Balance at beginning of period (in shares) at Mar. 31, 2018		55,968,481	3,845,496
Increase (Decrease) in Stockholders' Equity
Exercise of stock options awards	160	$ 0		160
Exercise of stock options awards (in shares)		84,535
Stock-based compensation expense	980			980
Common stock issued for settlement of restricted stock units net of shares withheld to satisfy income tax withholding obligations	(103)			(103)
Common stock issued for settlement of restricted stock units net of shares withheld to satisfy income tax withholding obligations (in shares)		206,248
Net loss	(3,119)					(3,119)
Foreign currency translation adjustment	(202)				(202)
Balance at end of period at Jun. 30, 2018	75,885	$ 5	$ (8,443)	290,516	(504)	(205,688)
Balance at end of period (in shares) at Jun. 30, 2018		56,259,264	3,845,496
Increase (Decrease) in Stockholders' Equity
Exercise of stock options awards	598	$ 0		598
Exercise of stock options awards (in shares)		392,488
Stock-based compensation expense	933			933
Common stock issued for settlement of restricted stock units net of shares withheld to satisfy income tax withholding obligations	(164)			(164)
Common stock issued for settlement of restricted stock units net of shares withheld to satisfy income tax withholding obligations (in shares)		68,004
Common stock issuance in connection with employee stock purchase plan	283			283
Common stock issuance in connection with employee stock purchase plan (in shares)		93,348
Net loss	(1,581)					(1,581)
Foreign currency translation adjustment	(145)				(145)
Balance at end of period at Sep. 30, 2018	75,809	$ 5	$ (8,443)	292,166	(649)	(207,269)
Balance at end of period (in shares) at Sep. 30, 2018		56,813,104	3,845,496
Balance at beginning of period at Dec. 31, 2018	54,395	$ 4	$ (31,980)	293,154	(949)	(205,834)
Balance at beginning of period (in shares) at Dec. 31, 2018		56,956,935	12,564,240
Increase (Decrease) in Stockholders' Equity
Exercise of stock options awards	3,181			3,181
Exercise of stock options awards (in shares)		825,349
Stock-based compensation expense	1,083			1,083
Common stock issued for settlement of restricted stock units net of shares withheld to satisfy income tax withholding obligations	(536)			(536)
Common stock issued for settlement of restricted stock units net of shares withheld to satisfy income tax withholding obligations (in shares)		280,808
Common stock issuance in connection with employee stock purchase plan	270			270
Common stock issuance in connection with employee stock purchase plan (in shares)		87,671
Net loss	(4,333)					(4,333)
Foreign currency translation adjustment	(232)				(232)
Balance at end of period at Mar. 31, 2019	53,828	$ 4	$ (31,980)	297,152	(1,181)	(210,167)
Balance at end of period (in shares) at Mar. 31, 2019		58,150,763	12,564,240
Balance at beginning of period at Dec. 31, 2018	54,395	$ 4	$ (31,980)	293,154	(949)	(205,834)
Balance at beginning of period (in shares) at Dec. 31, 2018		56,956,935	12,564,240
Increase (Decrease) in Stockholders' Equity
Net loss	(8,617)
Foreign currency translation adjustment	120
Balance at end of period at Sep. 30, 2019	56,136	$ 4	$ (31,980)	303,393	(829)	(214,452)
Balance at end of period (in shares) at Sep. 30, 2019		59,111,023	12,564,240
Balance at beginning of period at Mar. 31, 2019	53,828	$ 4	$ (31,980)	297,152	(1,181)	(210,167)
Balance at beginning of period (in shares) at Mar. 31, 2019		58,150,763	12,564,240
Increase (Decrease) in Stockholders' Equity
Exercise of stock options awards	611			611
Exercise of stock options awards (in shares)		149,478,000
Stock-based compensation expense	2,020			2,020
Common stock issued for settlement of restricted stock units net of shares withheld to satisfy income tax withholding obligations	(197)			(197)
Common stock issued for settlement of restricted stock units net of shares withheld to satisfy income tax withholding obligations (in shares)		74,768,000
Net loss	(1,484)					(1,484)
Foreign currency translation adjustment	212				212
Balance at end of period at Jun. 30, 2019	54,990	$ 4	$ (31,980)	299,586	(969)	(211,651)
Balance at end of period (in shares) at Jun. 30, 2019		58,375,009	12,564,240
Increase (Decrease) in Stockholders' Equity
Exercise of stock options awards	2,077			2,077
Exercise of stock options awards (in shares)		508,570,000
Stock-based compensation expense	1,868			1,868
Common stock issued for settlement of restricted stock units net of shares withheld to satisfy income tax withholding obligations	(377)			(377)
Common stock issued for settlement of restricted stock units net of shares withheld to satisfy income tax withholding obligations (in shares)		176,940,000
Common stock issuance in connection with employee stock purchase plan	239			239
Common stock issuance in connection with employee stock purchase plan (in shares)		50,504,000
Net loss	(2,801)					(2,801)
Foreign currency translation adjustment	140				140
Balance at end of period at Sep. 30, 2019	$ 56,136	$ 4	$ (31,980)	$ 303,393	$ (829)	$ (214,452)
Balance at end of period (in shares) at Sep. 30, 2019		59,111,023	12,564,240