Consolidated Statements of Stockholders' Equity (USD $) In Thousands	Common Stock [Member]	Treasury Stock [Member]	Additional Paid In Capital [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Income [Member]	Total
BALANCE at Dec. 31, 2009	$ 85	$ (25,260)	$ 266,472	$ 22,155	$ 24,168	$ 287,620
BALANCE (in shares) at Dec. 31, 2009	85,659	565
Amortization of stock compensation (Note 9)			7,594			7,594
Forfeitures			(288)			(288)
Forfeitures (in shares)	(454)
Exercises of stock options and issuance of restricted stock awards (Note 9)	3	3,673	3,515			7,191
Exercises of stock options and issuance of restricted stock awards (Note 9) (in shares)	2,908	(77)
Repurchase of common stock for tax withholding		(421)				(421)
Repurchase of common stock for tax withholding (in shares)	(47)	47
Net income (loss)				67,726		67,726
Foreign currency translation					9,048	9,048
Reclassification of cumulative foreign exchange translation adjustments to net income (Note 1)					(2,364)	(2,364)
BALANCE at Dec. 31, 2010	88	(22,008)	277,293	89,881	30,852	376,106
BALANCE (in shares) at Dec. 31, 2010	88,066	535
Amortization of stock compensation (Note 9)			8,928			8,928
Forfeitures			(435)			(435)
Forfeitures (in shares)	(149)
Exercises of stock options and issuance of restricted stock awards (Note 9)	2	2,739	8,173			10,914
Exercises of stock options and issuance of restricted stock awards (Note 9) (in shares)	1,912	(58)
Repurchase of common stock for tax withholding		(490)				(490)
Repurchase of common stock for tax withholding (in shares)	(22)	22
Net income (loss)				112,788		112,788
Foreign currency translation					(16,031)	(16,031)
BALANCE at Dec. 31, 2011	90	(19,759)	293,959	202,669	14,821	491,780
BALANCE (in shares) at Dec. 31, 2011	89,807	499
Amortization of stock compensation (Note 9)			11,764			11,764
Forfeitures			(493)			(493)
Forfeitures (in shares)	(43)
Exercises of stock options and issuance of restricted stock awards (Note 9)	1	1,112	2,593			3,706
Exercises of stock options and issuance of restricted stock awards (Note 9) (in shares)	783	(29)
Repurchase of common stock for tax withholding		(493)				(493)
Repurchase of common stock for tax withholding (in shares)		30
Purchase of treasury stock		(25,074)				(25,074)
Purchase of treasury stock (in shares)	(1,884)	1,884
Net income (loss)				131,343		131,343
Foreign currency translation					5,525	5,525
Reclassification of cumulative foreign exchange translation adjustments to net income (Note 1)					(658)	(658)
BALANCE at Dec. 31, 2012	$ 91	$ (44,214)	$ 307,823	$ 334,012	$ 19,688	$ 617,400
BALANCE (in shares) at Dec. 31, 2012	88,663	2,384