Consolidated Statements Stockholders' Equity (USD $)	Total	Common Stock	Treasury Stock	Additional Paid-in Capital	Retained Earnings	Accumulated Other Comprehensive Loss
Beginning Balance, Value at Dec. 31, 2010	$ 231,268,000	$ 3,602,000	$ (76,000)	$ 153,221,000	$ 67,642,000	$ 6,879,000
Beginning Balance, Issued Shares at Dec. 31, 2010		36,057,791
Beginning Balance, Treasury Shares at Dec. 31, 2010			(40,509)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	71,378,000				71,378,000
Cumulative translation adjustment	(11,403,000)					(11,403,000)
Exercise of stock options, Shares		69,509
Exercise of stock options, Value	51,000	8,000		43,000
Repurchase of common stock, Shares		(3,510,973)
Repurchase of common stock, Value	(63,659,000)	(351,000)		(63,308,000)
Settlement on conversion of convertible debt, Shares		0
Settlement on conversion of convertible debt, Value	(1,851,000)	0		(1,851,000)
Deferred compensation and amortization related to options and restricted stock	2,205,000			2,205,000
Business acquisition, number of common shares issued		3,650,914
Shares subscribed for business acquisition	87,476,000	365,000		87,111,000
APIC adjustment for stock options	2,111,000			2,111,000
Vesting of restricted stock, Shares		151,144
Vesting of restricted stock, Value	0	14,000		(14,000)
Forfeiture of certain shares to satisfy exercise costs and the recipients income tax obligations related to stock options exercised and restricted stock vested	0
Dividends paid	(1,461,000)				(1,461,000)
Ending Balance, Value at Dec. 31, 2011	316,115,000	3,638,000	(76,000)	179,518,000	137,559,000	(4,524,000)
Ending Balance, Issued Shares at Dec. 31, 2011		36,418,385
Ending Balance, Treasury Shares at Dec. 31, 2011			(40,509)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	70,569,000				70,569,000
Cumulative translation adjustment	(2,394,000)					(2,394,000)
Exercise of stock options, Shares		1,361,542
Exercise of stock options, Value	1,020,000	137,000		883,000
Repurchase of common stock, Shares		(983,818)
Repurchase of common stock, Value	(18,374,000)	(99,000)		(18,275,000)
Deferred compensation and amortization related to options and restricted stock	2,083,000			2,083,000
Share subscribed for business acquisition, Shares		296,560
Equity instruments	0	30,000		(30,000)
APIC adjustment for stock options	1,162,000			1,162,000
Vesting of restricted stock, Shares		89,308
Vesting of restricted stock, Value	0	8,000		(8,000)
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	(992,000)	(5,000)		(987,000)
Dividends paid	(7,034,000)				(7,034,000)
Ending Balance, Value at Dec. 31, 2012	362,155,000	3,709,000	(76,000)	164,346,000	201,094,000	(6,918,000)
Ending Balance, Issued Shares at Dec. 31, 2012	37,131,777	37,131,777
Ending Balance, Treasury Shares at Dec. 31, 2012			(40,509)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	59,274,000				59,274,000
Cumulative translation adjustment	(5,376,000)					(5,376,000)
Exercise of stock options, Shares		1,251,633
Exercise of stock options, Value	2,161,000	125,000		2,036,000
Repurchase of common stock, Shares		(250,900)
Repurchase of common stock, Value	(2,492,000)	(25,000)		(2,467,000)
Deferred compensation and amortization related to options and restricted stock	1,941,000			1,941,000
APIC adjustment for stock options	37,000			37,000
Vesting of restricted stock, Shares		76,576
Vesting of restricted stock, Value	0	8,000		(8,000)
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	(1,681,000)	(12,000)		(1,669,000)
Dividends paid	(2,794,000)				(2,794,000)
Ending Balance, Value at Dec. 31, 2013	$ 413,225,000	$ 3,805,000	$ (76,000)	$ 164,216,000	$ 257,574,000	$ (12,294,000)
Ending Balance, Issued Shares at Dec. 31, 2013	38,088,391	38,088,391
Ending Balance, Treasury Shares at Dec. 31, 2013			(40,509)