Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Total	Interest Rate Cap [Member]	Interest Rate Swap [Member]	Common Stock (0.01 Par) [Member]	Additional Paid-in Capital [Member]	Retained Earnings (Accumulated Deficit)	Treasury Stock at Cost [Member]	Accumulated Other Comprehensive Loss [Member]	Accumulated Other Comprehensive Loss [Member] Interest Rate Cap [Member]	Accumulated Other Comprehensive Loss [Member] Interest Rate Swap [Member]
Balance at Dec. 31, 2015	$ 158,344			$ 172	$ 105,872	$ 73,598	$ (8,497)	$ (12,801)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	20,247					20,247
Foreign currency translation adjustments	(8,661)							(8,661)
Repurchases of common stock in the open market	(7,959)						(7,959)
Stock-based compensation expense	3,229				3,229
Income tax benefit from stock-based compensation	137				137
Shares withheld in exchange for tax withholding payments on stock-based compensation	(771)				(771)
Issuance of stock for employer contributions to retirement plan	2,708				(34)		2,742
Net issuances of stock pursuant to stock compensation plans and other	222				(1,864)		2,086
Balance at Dec. 31, 2016	167,496			172	106,569	93,845	(11,628)	(21,462)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Adjusted balance	167,593			172	106,803	93,708	(11,628)	(21,462)
Net income	12,891					12,891
Foreign currency translation adjustments	6,686							6,686
Change in fair value of derivative instrument, net of tax		$ (142)	$ 63						$ (142)	$ 63
Repurchases of common stock in the open market	(4,302)						(4,302)
Stock-based compensation expense	3,589				3,589
Shares withheld in exchange for tax withholding payments on stock-based compensation	(1,168)				(1,168)
Issuance of stock for employer contributions to retirement plan	2,725				40		2,685
Net issuances of stock pursuant to stock compensation plans and other	119				(2,008)		2,127
Balance at Dec. 31, 2017	188,054			172	107,256	106,599	(11,118)	(14,855)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Adjusted balance	187,658			172	107,256	106,203	(11,118)	(14,855)
Net income	9,836					9,836
Foreign currency translation adjustments	(6,914)							(6,914)
Change in fair value of derivative instrument, net of tax		$ 142	$ (63)						$ 142	$ (63)
Repurchases of common stock in the open market	(7,993)						(7,993)
Stock-based compensation expense	1,350				1,350
Shares withheld in exchange for tax withholding payments on stock-based compensation	(416)				(416)
Issuance of stock for employer contributions to retirement plan	2,960				(867)		3,827
Net issuances of stock pursuant to stock compensation plans and other	9				(1,473)		1,482
Balance at Dec. 31, 2018	$ 186,569			$ 172	$ 105,850	$ 116,039	$ (13,802)	$ (21,690)