Consolidated Statements of Stockholders' Equity - USD ($) shares in Thousands, $ in Thousands	Total	Common Stock [Member]	Additional Paid in Capital [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Redeemable Non-Controlling Interest [Member]
Beginning balance at Dec. 31, 2014	$ 258,759	$ 26	$ 139,087	$ 161,061	$ (41,415)	$ 883
Beginning balance (in shares) at Dec. 31, 2014		26,354
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation and vesting of restricted stock	2,822		2,822
Stock-based compensation and vesting of restricted stock (in shares)		82
Net income	35,406			35,406
Net loss attributable to non-controlling interest	63					(63)
Purchase of non-controlling interest	(187)		223		(410)	(691)
Dividends declared	(14,928)			(14,928)
Change in fair value of interest rate swap, net of tax	(283)				(283)
Minimum Pension adjustment, net of tax	(989)				(989)
Repurchases of common stock	(17,298)		(17,298)
Repurchases of common stock (in shares)		(663)
Cumulative foreign currency translation adjustment, net of tax	(20,735)				(20,735)	(129)
Ending balance at Dec. 31, 2015	242,567	$ 26	124,834	181,539	(63,832)
Ending balance (in shares) at Dec. 31, 2015		25,773
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cumulative foreign currency translation adjustment, net of tax	(20,735)				(20,735)	$ (129)
Stock-based compensation and vesting of restricted stock	2,893		2,893
Stock-based compensation and vesting of restricted stock (in shares)		74
Net income	25,140			25,140
Conversion of Convertible Debt	45,286	$ 1	45,285
Conversion of Convertible Debt (in shares)		1,536
Dividends declared	(15,571)			(15,571)
Change in fair value of interest rate swap, net of tax	(506)				(506)
Minimum Pension adjustment, net of tax	139				139
Repurchases of common stock	(4,713)		(4,713)
Repurchases of common stock (in shares)		(177)
Cumulative foreign currency translation adjustment, net of tax	(11,887)				(11,887)
Ending balance at Dec. 31, 2016	283,348	$ 27	168,299	191,108	(76,086)
Ending balance (in shares) at Dec. 31, 2016		27,206
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cumulative foreign currency translation adjustment, net of tax	(11,887)				(11,887)
Stock-based compensation and vesting of restricted stock	3,186		3,186
Stock-based compensation and vesting of restricted stock (in shares)		104
Net income	51,427			51,427
Conversion of Convertible Debt	51,853	$ 2	51,851
Conversion of Convertible Debt (in shares)		1,748
Dividends declared	(19,331)			(19,331)
Change in fair value of interest rate swap, net of tax	194				194
Minimum Pension adjustment, net of tax	1,990				1,990
Cumulative foreign currency translation adjustment, net of tax	24,038				24,038
Ending balance at Dec. 31, 2017	396,705	$ 29	$ 223,336	$ 223,204	(49,864)
Ending balance (in shares) at Dec. 31, 2017		29,058
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cumulative foreign currency translation adjustment, net of tax	$ 24,038				$ 24,038