CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY (USD $) Share data in Thousands, unless otherwise specified	Total	Common Stock	Treasury Stock	Shares Held Under Employee Participation Plan	Additional Paid-in Capital	Comprehensive Income	Accumulated Other Comprehensive Income	Accumulated Earnings
Balance at Dec. 31, 2008	$ 429,045,000	$ 474,000	$ (1,653,000)		$ 353,713,000		$ (688,000)	$ 77,199,000
Balance (in shares) at Dec. 31, 2008		47,466
Increase (Decrease) in Stockholders' Equity
Net income	36,686,000					36,686,000		36,686,000
Change in fair value of available for sale securities, net of taxes	1,726,000					1,726,000	1,726,000
Foreign currency translation	25,259,000					25,259,000	25,259,000
Unfunded Pension liability (net of deferred taxes)	532,000					532,000	532,000
Comprehensive income						64,203,000
Exercise of Warrants (in Shares)		66
Exercise of warrants	525,000				525,000
Stock-based compensation	(415,000)		(415,000)
Stock-based compensation (in shares)		(16)
Shares held under employee participation plan	(1,150,000)			(1,150,000)
Exercise of stock options	430,000	2,000			428,000
Exercise of stock options (in shares)		58
Issuance of common stock, net of issuance costs of $556	118,398,000	48,000			118,350,000
Issuance of common stock, net of issuance costs of $556 (in shares)		4,784
Net tax benefit on exercise of stock options	474,000				474,000
Employee stock purchase plan	2,315,000				2,315,000
Employee stock purchase plan (in shares)		104
Balance at Dec. 31, 2009	613,825,000	524,000	(2,068,000)	(1,150,000)	475,805,000		26,829,000	113,885,000
Balance (in shares) at Dec. 31, 2009		52,462
Increase (Decrease) in Stockholders' Equity
Net income	130,515,000					130,515,000		130,515,000
Change in fair value of available for sale securities, net of taxes	(551,000)					(551,000)	(551,000)
Foreign currency translation	24,536,000					24,536,000	24,536,000
Unfunded Pension liability (net of deferred taxes)	(55,000)					(55,000)	(55,000)
Comprehensive income						154,445,000
Stock-based compensation	6,518,000				6,518,000
Stock-based compensation (in shares)		48
Shares held under employee participation plan	373,000			373,000
Issuance of restricted shares, net of shares remitted	(399,000)		(399,000)
Issuance of restricted shares, net of shares remitted (in shares)		(12)
Exercise of stock options	862,000	4,000			858,000
Exercise of stock options (in shares)		142
Issuance of acquisition-related common stock, net of issuance costs	1,015,000				1,015,000
Issuance of acquisition-related common stock, net of issuance costs (in shares)		32
Net tax benefit on exercise of stock options	1,739,000				1,739,000
Employee stock purchase plan	2,449,000				2,449,000
Employee stock purchase plan (in shares)		100
Balance at Dec. 31, 2010	780,827,000	528,000	(2,467,000)	(777,000)	488,384,000		50,759,000	244,400,000
Balance (in shares) at Dec. 31, 2010		52,772
Increase (Decrease) in Stockholders' Equity
Net income	127,252,000					127,252,000		127,252,000
Treasury Stock, Retired, Cost Method, Amount			2,467,000		(2,467,000)
Change in fair value of available for sale securities, net of taxes	686,000					686,000	686,000
Realized Investment Gains (Losses)	(1,493,000)					(1,493,000)	(1,493,000)
Foreign currency translation	(18,264,000)					(18,264,000)	(18,264,000)
Unfunded Pension liability (net of deferred taxes)	(335,000)					(335,000)	(335,000)
Comprehensive income						107,846,000
Stock-based compensation	7,854,000		0		7,854,000
Stock-based compensation (in shares)		322
Shares held under employee participation plan	308,000			308,000
Issuance of restricted shares, net of shares remitted	(4,061,000)		0
Issuance of restricted shares, net of shares remitted (in shares)		(76)			(4,061)
Exercise of stock options	1,350,000	4,000			1,346,000
Exercise of stock options (in shares)	71,450	71
Net tax benefit on exercise of stock options	3,347,000				3,347,000
Employee stock purchase plan	3,516,000				3,516,000
Employee stock purchase plan (in shares)		94
Balance at Dec. 31, 2011	$ 900,987,000	$ 532,000	$ 0	$ (469,000)	$ 497,919,000		$ 31,353,000	$ 371,652,000
Balance (in shares) at Dec. 31, 2011		53,183