Condensed Consolidated Statement of Stockholders' Equity (Unaudited) - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-in Capital	Retained Earnings	Noncontrolling Interest [Member]	Accumulated Other Comprehensive Loss
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	$ 533,759
New Accounting Pronouncement or Change in Accounting Principle, Effect of Adoption, Quantification	11,600
New Accounting Pronouncement or Change in Accounting Principle, Effect of Adoption, Quantification | Calculated under Revenue Guidance in Effect before Topic 606 [Member]	(8,802)			$ (8,802)
New Accounting Pronouncement or Change in Accounting Principle, Effect of Adoption, Quantification | ASC 340-40 [Member]	$ (1,460)			(1,460)
Beginning Balance, Issued Shares at Dec. 31, 2017	31,476,428	31,476,428
Beginning Balance, Value at Dec. 31, 2017	$ 491,510	$ 3,148	$ 1,410	510,975	$ 42,249	$ (24,023)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income (Loss) Attributable to Parent	55,388			55,388
Net Income (Loss) Attributable to Noncontrolling Interest	139				139
Cumulative translation adjustment	(30,937)					(30,937)
Repurchase and retirement of common stock, Shares		(30,000)
Repurchase and retirement of common stock, Value	(2,226)	$ (3)	(1,339)	(884)
Vesting of restricted stock, Shares		25,957
Vesting of restricted stock, Value	0	$ 1	(1)
Share based compensation	1,509		1,509
Forfeiture of certain shares to satisfy exercise costs and the recipients income tax obligations related to stock options exercised and restricted stock vested, Shares		(1,014)
Forfeiture of certain shares to satisfy exercise costs and the recipients income tax obligations related to stock options exercised and restricted stock vested	(100)	$ 0	(100)
Recognized controlling ownership of joint venture	5,327		(787)		6,114
Dividends paid	$ (4,737)			(4,737)
Ending Balance, Issued Shares at Jun. 30, 2018	31,473,654	31,473,654
Ending Balance, Value at Jun. 30, 2018	$ 499,400	$ 3,146	$ 734	$ 550,480	$ 48,502	$ (54,960)
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	$ 547,902