Consolidated Statements Stockholders' Equity (USD $) In Thousands, except Share data, unless otherwise specified	Total	Common Stock	Treasury Stock	Additional Paid-in Capital	Retained Earnings	Accumulated Other Comprehensive Loss
Beginning Balance, Value at Dec. 31, 2011	$ 316,115	$ 3,638	$ (76)	$ 179,518	$ 137,559	$ (4,524)
Beginning Balance, Issued Shares at Dec. 31, 2011		36,418,385
Beginning Balance, Treasury Shares at Dec. 31, 2011			(40,509)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	70,569				70,569
Cumulative translation adjustment	(2,394)					(2,394)
Exercise of stock options, Shares		1,361,542
Exercise of stock options	1,020	137		883
Deferred compensation and amortization related to options and restricted stock	2,083			2,083
Shares subscribed for business acquisition, Shares		296,560
Shares subscribed for business acquisition	0	30		(30)
Repurchase of common stock, Shares		(983,818)
Repurchase of common stock	(18,374)	(99)		(18,275)
APIC adjustment for stock options	1,162			1,162
Vesting of restricted stock, Shares		89,308
Vesting of restricted stock	0	8		(8)
Forfeiture of certain shares to satisfy exercise costs and the recipients income tax obligations related to stock options exercised and restricted stock vested, Shares		(50,200)
Forfeiture of certain shares to satisfy exercise costs and the recipients income tax obligations related to stock options exercised and restricted stock vested	(992)	(5)		(987)
Dividends paid	(7,034)				(7,034)
Ending Balance, Value at Dec. 31, 2012	362,155	3,709	(76)	164,346	201,094	(6,918)
Ending Balance, Issued Shares at Dec. 31, 2012		37,131,777
Ending Balance, Treasury Shares at Dec. 31, 2012			(40,509)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	59,274				59,274
Cumulative translation adjustment	(5,376)					(5,376)
Exercise of stock options, Shares		1,251,633
Exercise of stock options	2,161	125		2,036
Deferred compensation and amortization related to options and restricted stock	1,941			1,941
Repurchase of common stock, Shares		(250,900)
Repurchase of common stock	(2,492)	(25)		(2,467)
APIC adjustment for stock options	37			37
Vesting of restricted stock, Shares		76,576
Vesting of restricted stock	0	8		(8)
Forfeiture of certain shares to satisfy exercise costs and the recipients income tax obligations related to stock options exercised and restricted stock vested, Shares		(120,695)
Forfeiture of certain shares to satisfy exercise costs and the recipients income tax obligations related to stock options exercised and restricted stock vested	(1,681)	(12)		(1,669)
Dividends paid	(2,794)				(2,794)
Ending Balance, Value at Dec. 31, 2013	413,225	3,805	(76)	164,216	257,574	(12,294)
Ending Balance, Issued Shares at Dec. 31, 2013	38,088,391	38,088,391
Ending Balance, Treasury Shares at Dec. 31, 2013			(40,509)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	63,558				63,558
Cumulative translation adjustment	(5,855)					(5,855)
Exercise of stock options, Shares		450,000
Exercise of stock options	788	45		743
Deferred compensation and amortization related to options and restricted stock	1,792			1,792
Repurchase of common stock, Shares		(2,146,488)
Repurchase of common stock	(31,854)	(215)		(31,639)
Vesting of restricted stock, Shares		52,384
Vesting of restricted stock	0	5		(5)
Forfeiture of certain shares to satisfy exercise costs and the recipients income tax obligations related to stock options exercised and restricted stock vested, Shares		(2,557)
Forfeiture of certain shares to satisfy exercise costs and the recipients income tax obligations related to stock options exercised and restricted stock vested	(41)	0		(41)
Shares reaquired in connection with put option, Shares		(209,656)
Shares reaquired in connection with put option	(2,986)	(21)		(2,965)
Reclassification of shares previously reported as temporary equity in connection with an acquisition	5,000			5,000
Dividends paid	(11,406)				(11,406)
Ending Balance, Value at Dec. 31, 2014	$ 432,221	$ 3,619	$ (76)	$ 137,101	$ 309,726	$ (18,149)
Ending Balance, Issued Shares at Dec. 31, 2014	36,232,074	36,232,074
Ending Balance, Treasury Shares at Dec. 31, 2014			(40,509)