Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Total	Interest Rate Cap [Member]	Interest Rate Swap [Member]	Common Stock (0.01 Par) [Member]	Common Stock (0.01 Par) [Member] Interest Rate Cap [Member]	Common Stock (0.01 Par) [Member] Interest Rate Swap [Member]	Additional Paid-in Capital [Member]	Additional Paid-in Capital [Member] Interest Rate Cap [Member]	Additional Paid-in Capital [Member] Interest Rate Swap [Member]	Retained Earnings (Accumulated Deficit)	Retained Earnings (Accumulated Deficit) Interest Rate Cap [Member]	Retained Earnings (Accumulated Deficit) Interest Rate Swap [Member]	Treasury Stock at Cost [Member]	Treasury Stock at Cost [Member] Interest Rate Cap [Member]	Treasury Stock at Cost [Member] Interest Rate Swap [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, 2014	$ 151,725			$ 171			$ 104,523			$ 54,809			$ (381)			$ (7,397)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	18,789			0			0			18,789			0			0
Foreign currency translation adjustments	(5,404)			0			0			0			0			(5,404)
Repurchases of common stock in the open market	(12,347)			0			0			0			(12,347)			0
Stock-based compensation expense	3,050			0			3,050			0			0			0
Income tax benefit from stock-based compensation	835			0			835			0			0			0
Shares withheld in exchange for tax withholding payments on stock-based compensation	(1,451)			0			(1,451)			0			0			0
Issuance of stock for employer contributions to retirement plan	2,711			1			681			0			2,029			0
Net issuances of stock pursuant to stock compensation plans and other	436			0			(1,766)			0			2,202			0
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			0			0			20,247			0			0
Foreign currency translation adjustments	(8,661)			0			0			0			0			(8,661)
Repurchases of common stock in the open market	(7,959)			0			0			0			(7,959)			0
Stock-based compensation expense	3,229			0			3,229			0			0			0
Income tax benefit from stock-based compensation	137			0			137			0			0			0
Shares withheld in exchange for tax withholding payments on stock-based compensation	(771)			0			(771)			0			0			0
Issuance of stock for employer contributions to retirement plan	2,708			0			(34)			0			2,742			0
Net issuances of stock pursuant to stock compensation plans and other	222			0			(1,864)			0			2,086			0
Balance at Dec. 31, 2016	167,496			172			106,569			93,845			(11,628)			(21,462)
Adjusted balance at December 31, 2016	167,593			172			106,803			93,708			(11,628)			(21,462)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	12,891			0			0			12,891			0			0
Foreign currency translation adjustments	6,686			0			0			0			0			6,686
Change in fair value of derivative instrument, net of tax		$ (142)	$ 63		$ 0	$ 0		$ 0	$ 0		$ 0	$ 0		$ 0	$ 0		$ (142)	$ 63
Repurchases of common stock in the open market	(4,302)			0			0			0			(4,302)			0
Stock-based compensation expense	3,589			0			3,589			0			0			0
Shares withheld in exchange for tax withholding payments on stock-based compensation	(1,168)			0			(1,168)			0			0			0
Issuance of stock for employer contributions to retirement plan	2,725			0			40			0			2,685			0
Net issuances of stock pursuant to stock compensation plans and other	119			0			(2,008)			0			2,127			0
Balance at Dec. 31, 2017	$ 188,054			$ 172			$ 107,256			$ 106,599			$ (11,118)			$ (14,855)