CONSOLIDATED STATEMENTS OF STOCKHOLDERS’ EQUITY - USD ($) shares in Thousands, $ in Thousands	Total	Common Stock Issued	Common Stock in Treasury	Paid-in Capital	Accumulated Other Comprehensive Income (Loss)	Retained Earnings
Balance (in shares) at Dec. 31, 2017		23,760	(9,703)
Balance at Dec. 31, 2017	$ 253,549	$ 238	$ (262,065)	$ 265,195	$ (16,599)	$ 266,780
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	(587)					(587)
Currency translation adjustment	3,646				3,646
Shares issued for employee benefit plan and compensation (in shares)		42
Shares issued for employee benefit plan and compensation	336	$ 0		336
Purchase of treasury shares (in shares)			(13)
Purchase of treasury shares	(615)		$ (615)
Stock options exercised (in shares)		20
Stock options exercised	439	$ 0		439
Shares issued to directors (in shares)		8
Shares issued to directors	0	$ 0		0
Employee and director stock-based compensation	2,204			2,204
Performance - based common stock warrants	471			471
Balance (in shares) at Mar. 31, 2018		23,830	(9,716)
Balance at Mar. 31, 2018	263,527	$ 238	$ (262,680)	268,645	(12,953)	270,277
Balance (in shares) at Dec. 31, 2017		23,760	(9,703)
Balance at Dec. 31, 2017	253,549	$ 238	$ (262,065)	265,195	(16,599)	266,780
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	23,031
Currency translation adjustment	$ (5,190)
Purchase of treasury shares (in shares)	(373)
Purchase of treasury shares	$ (12,564)
Balance (in shares) at Sep. 30, 2018		23,892	(10,076)
Balance at Sep. 30, 2018	272,209	$ 239	$ (274,629)	274,493	(21,789)	293,895
Balance (in shares) at Mar. 31, 2018		23,830	(9,716)
Balance at Mar. 31, 2018	263,527	$ 238	$ (262,680)	268,645	(12,953)	270,277
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	22,659					22,659
Currency translation adjustment	(5,058)				(5,058)
Shares issued for employee benefit plan and compensation (in shares)		14
Shares issued for employee benefit plan and compensation	254	$ 1		253
Purchase of treasury shares (in shares)			(212)
Purchase of treasury shares	(6,499)		$ (6,499)
Stock options exercised (in shares)		10
Stock options exercised	265	$ 0		265
Shares issued to directors (in shares)		8
Shares issued to directors	0	$ 0		0
Employee and director stock-based compensation	2,465			2,465
Performance - based common stock warrants	(128)			(128)
Balance (in shares) at Jun. 30, 2018		23,862	(9,928)
Balance at Jun. 30, 2018	277,485	$ 239	$ (269,179)	271,500	(18,011)	292,936
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	959					959
Currency translation adjustment	(3,778)				(3,778)
Shares issued for employee benefit plan and compensation (in shares)		18
Shares issued for employee benefit plan and compensation	290	$ 0		290
Purchase of treasury shares (in shares)			(148)
Purchase of treasury shares	(5,450)		$ (5,450)
Stock options exercised (in shares)		5
Stock options exercised	160	$ 0		160
Shares issued to directors (in shares)		7
Shares issued to directors	0	$ 0
Employee and director stock-based compensation	2,139			2,139
Performance - based common stock warrants	404			404
Balance (in shares) at Sep. 30, 2018		23,892	(10,076)
Balance at Sep. 30, 2018	272,209	$ 239	$ (274,629)	274,493	(21,789)	293,895
Balance (in shares) at Dec. 31, 2018		23,933	(10,116)
Balance at Dec. 31, 2018	262,960	$ 239	$ (275,889)	276,103	(20,281)	282,788
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	(1,005)					(1,005)
Currency translation adjustment	1,733				1,733
Shares issued for employee benefit plan and compensation (in shares)		78
Shares issued for employee benefit plan and compensation	347	$ 1		346
Purchase of treasury shares (in shares)			(43)
Purchase of treasury shares	(1,215)		$ (1,215)
Shares issued to directors (in shares)		8
Shares issued to directors	0	$ 0		0
Employee and director stock-based compensation	1,918			1,918
Performance - based common stock warrants	434			434
Balance (in shares) at Mar. 31, 2019		24,019	(10,159)
Balance at Mar. 31, 2019	265,172	$ 240	$ (277,104)	278,801	(18,548)	281,783
Balance (in shares) at Dec. 31, 2018		23,933	(10,116)
Balance at Dec. 31, 2018	262,960	$ 239	$ (275,889)	276,103	(20,281)	282,788
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	(3,397)
Currency translation adjustment	$ (5,557)
Purchase of treasury shares (in shares)	(55)
Purchase of treasury shares	$ (1,741)
Stock options exercised (in shares)	20
Balance (in shares) at Sep. 30, 2019		24,099	(10,171)
Balance at Sep. 30, 2019	$ 261,651	$ 241	$ (277,630)	285,487	(25,838)	279,391
Balance (in shares) at Mar. 31, 2019		24,019	(10,159)
Balance at Mar. 31, 2019	265,172	$ 240	$ (277,104)	278,801	(18,548)	281,783
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	(5,061)					(5,061)
Currency translation adjustment	(1,833)				(1,833)
Shares issued for employee benefit plan and compensation (in shares)		17
Shares issued for employee benefit plan and compensation	273	$ 0		273
Purchase of treasury shares (in shares)			(5)
Purchase of treasury shares	(189)		$ (189)
Shares issued to directors (in shares)		7
Shares issued to directors	0	$ 0		0
Employee and director stock-based compensation	2,273			2,273
Performance - based common stock warrants	236			236
Balance (in shares) at Jun. 30, 2019		24,043	(10,164)
Balance at Jun. 30, 2019	260,871	$ 240	$ (277,293)	281,583	(20,381)	276,722
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	2,669					2,669
Currency translation adjustment	(5,457)				(5,457)
Shares issued for employee benefit plan and compensation (in shares)		29
Shares issued for employee benefit plan and compensation	256	$ 1		255
Purchase of treasury shares (in shares)			(7)
Purchase of treasury shares	(337)		$ (337)
Stock options exercised (in shares)		20
Stock options exercised	411			411
Shares issued to directors (in shares)		7
Shares issued to directors	0	$ 0		0
Employee and director stock-based compensation	2,527			2,527
Performance - based common stock warrants	711			711
Balance (in shares) at Sep. 30, 2019		24,099	(10,171)
Balance at Sep. 30, 2019	$ 261,651	$ 241	$ (277,630)	$ 285,487	$ (25,838)	$ 279,391