Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Total	Common Stock	Treasury Stock	Additional Paid-in Capital	Accumulated Other Comprehensive Income (Loss)	Retained Earnings
Balance at Dec. 31, 2014	$ 292,980	$ 6	$ (49,996)	$ 207,429	$ (5,401)	$ 140,942
Balance (in shares) at Dec. 31, 2014		61,852,000	9,021,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	(33,063)
Total other comprehensive loss	(8,592)
Foreign currency translation adjustments					(8,592)
Comprehensive income (loss)	(41,655)
Issuance of common stock upon exercise of stock awards	$ 675	$ 0		675
Issuance of common stock upon exercise of stock awards (in shares)	405,000	793,000
Issuance of common stock and treasury shares as consideration for acquisition	$ 1,571		$ 2,686			(1,115)
Issuance of treasury shares as consideration for acquisition (in shares)			238,000
Acquisition of treasury shares	(4,897)
Excess tax benefit derived from stock award exercises	(411)			(411)
Stock-based compensation expense	5,873			5,873
Balance at Dec. 31, 2015	254,136	$ 6	$ (52,207)	213,566	(13,993)	106,764
Balance (in shares) at Dec. 31, 2015		62,645,000	9,547,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	4,370
Total other comprehensive loss	(6,806)
Foreign currency translation adjustments	(7,168)
Comprehensive income (loss)	(2,436)
Issuance of common stock upon exercise of stock awards	$ 1,770	$ 0		1,770
Issuance of common stock upon exercise of stock awards (in shares)	420,000	746,000
Issuance of common stock and treasury shares as consideration for acquisition	$ 2,012		$ 2,749			(737)
Issuance of treasury shares as consideration for acquisition (in shares)			244,000
Acquisition of treasury shares (in shares)	1,121,928
Acquisition of treasury shares	$ (11,000)
Excess tax benefit derived from stock award exercises	3,572			3,572
Stock-based compensation expense	5,572			5,572
Balance at Dec. 31, 2016	264,626	$ 6	$ (49,458)	224,480	(20,799)	110,397
Balance (in shares) at Dec. 31, 2016		63,391,000	9,303,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	18,979
Total other comprehensive loss	1,719
Foreign currency translation adjustments	1,732
Comprehensive income (loss)	20,697
Issuance of common stock upon exercise of stock awards	$ 1,421	$ 0		1,421
Issuance of common stock upon exercise of stock awards (in shares)	428,000	648,000
Issuance of common stock and treasury shares as consideration for acquisition	$ 4,678	$ 0	$ 4,561	385		(269)
Issuance of treasury shares as consideration for acquisition (in shares)		(36,000)	405,000
Acquisition of treasury shares (in shares)			1,122,000
Acquisition of treasury shares	(10,976)		$ (10,976)
Stock-based compensation expense	6,820			6,820
New Accounting Pronouncement or Change in Accounting Principle, Effect of Adoption, Quantification	2,291			2,093		198
Balance at Dec. 31, 2017	$ 289,559	$ 6	$ (55,873)	$ 235,199	$ (19,079)	$ 129,305
Balance (in shares) at Dec. 31, 2017		64,075,000	10,020,000