Consolidated Statements of Changes in Stockholders' Equity - USD ($) $ in Thousands	Total	Common Stock	Treasury Stock	Additional Paid-In Capital	Accumulated Other Comprehensive Income (Loss)	Accumulated Deficit
Beginning balance at Dec. 31, 2015	$ 101,432	$ 5	$ 0	$ 279,136	$ (55)	$ (177,654)
Beginning balance (shares) at Dec. 31, 2015		52,214,384	0
Increase (Decrease) in Stockholders' Equity
Exercise of warrants and stock options awards	161			161
Exercise of stock options awards (shares)		167,367
Stock-based compensation expense	3,895			3,895
Common stock issued for settlement of restricted stock units net of shares withheld to satisfy income tax withholding obligations	(205)			(205)
Common stock issued for settlement of restricted stock units net of shares withheld to satisfy income tax withholding obligations (shares)		560,922
Common stock issuance in connection with employee stock purchase plan	499			499
Common stock issuance in connection with employee stock purchase plan (shares)		350,283
Treasury stock — repurchase of stock	$ (6,037)		$ (6,037)
Treasury stock — repurchase of stock (shares)	(2,861,632)		(2,861,632)
Net income (loss)	$ (20,947)					(20,947)
Foreign currency translation adjustment	(276)				(276)
Ending balance at Dec. 31, 2016	78,522	$ 5	$ (6,037)	283,486	(331)	(198,601)
Ending balance (shares) at Dec. 31, 2016		53,292,956	(2,861,632)
Increase (Decrease) in Stockholders' Equity
Exercise of warrants and stock options awards	$ 699			699
Exercise of stock options awards (shares)	439,385	439,791
Stock-based compensation expense	$ 5,394			5,394
Common stock issued for settlement of restricted stock units net of shares withheld to satisfy income tax withholding obligations	(1,842)			(1,842)
Common stock issued for settlement of restricted stock units net of shares withheld to satisfy income tax withholding obligations (shares)		1,124,380
Common stock issuance in connection with employee stock purchase plan	446			446
Common stock issuance in connection with employee stock purchase plan (shares)		278,911
Treasury stock — repurchase of stock	$ (2,406)		$ (2,406)
Treasury stock — repurchase of stock (shares)	(983,864)		(983,864)
Retroactive application of ASU 2016-09	$ 0			94		(94)
Net income (loss)	2,227					2,227
Foreign currency translation adjustment	99				99
Ending balance at Dec. 31, 2017	$ 83,139	$ 5	$ (8,443)	$ 288,277	$ (232)	$ (196,468)
Ending balance (shares) at Dec. 31, 2017		55,136,038	(3,845,496)