Consolidated Statements of Equity - USD ($) shares in Thousands, $ in Thousands	Total	Common Stock	Additional Paid-in Capital	Accumulated Other Comprehensive Income (Loss)	Note Receivable Collateralized By Stock	Treasury Stock	Retained Earnings
Balances at Dec. 31, 2014	$ 127,073	$ 33	$ 85,154	$ (895)	$ (348)	$ (19,576)	$ 62,705
Balances (in shares) at Dec. 31, 2014		32,686
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	15,587
Other comprehensive income	(702)			(702)
Purchase of shares of treasury stock	(14,930)					(14,930)
Foreclosure of 80 shares of stock collateralizing note receivable	(340)				348	(688)
Option exercises	168	$ 0	168
Option exercises (in shares)		118
Warrant exercises	38	$ 0	38
Warrant exercises (in shares)		45
Restricted stock release	0	$ 0
Restricted stock release (in shares)		349
Consideration for acquisition of patent	198	$ 0	198
Consideration for acquisition of patent (in shares)		21
Stock-based compensation expense	3,893		3,893
Payment of withholding taxes on restricted stock units	(724)		(724)
Excess tax benefit (shortfall) related to share-based payments	256		256
Balances at Dec. 31, 2015	130,517	$ 33	88,983	(1,597)	0	(35,194)	78,292
Balances (in shares) at Dec. 31, 2015		33,219
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	(15,587)
Other comprehensive income	(517)			(517)
Purchase of shares of treasury stock	(951)					(951)
Option exercises	0	$ 0
Option exercises (in shares)		21
Warrant exercises	54	$ 0	54
Warrant exercises (in shares)		7
Restricted stock release	1	$ 1
Restricted stock release (in shares)		589
Employee stock purchase plan release	0	$ 0
Employee stock purchase plan release (in shares)		4
Stock-based compensation expense	3,830		3,830
Payment of withholding taxes on restricted stock units	(630)		(630)
Excess tax benefit (shortfall) related to share-based payments	545		545
Balances at Dec. 31, 2016	117,262	$ 34	92,782	(2,114)	0	(36,145)	62,705
Balances (in shares) at Dec. 31, 2016		33,840
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	15,100
Other comprehensive income	1,766			1,766
Purchase of shares of treasury stock	(1,492)					(1,492)
Restricted stock release	0	$ 0
Restricted stock release (in shares)		262
Employee stock purchase plan release	29	$ 0	29
Employee stock purchase plan release (in shares)		2
Stock-based compensation expense	3,602		3,602
Payment of withholding taxes on restricted stock units	(268)		(268)
Balances at Dec. 31, 2017	$ 135,999	$ 34	$ 96,145	$ (348)	$ 0	$ (37,637)	$ 77,805
Balances (in shares) at Dec. 31, 2017		34,104