Consolidated Statements of Shareholders' Equity (USD $) In Thousands	Total	Treasury Stock	Common Stock	Additional Paid-in Capital	Retained Earnings	Accumulated Other Comprehensive (Loss) Income Foreign Currency Translation	Accumulated Other Comprehensive (Loss) Income Available-for-Sale Investments	Accumulated Other Comprehensive (Loss) Income Cash Flow Hedges
Beginning Balance at Dec. 31, 2009		$ (49,375)	$ 45,378	$ 196,669	$ 694,689	$ (13)	$ (88)
Beginning Balance (in shares) at Dec. 31, 2009		(9,398)
Dividends, $.049 and $.054 per share in 2010 and 2011 respectively					(3,981)
Stock-Based Compensation				4,759
Reissued Shares (in shares)		212
Reissued Shares		743		324
Repurchased Shares (in shares)		(1,479)
Repurchased Shares		(29,009)
Stock Recombination			(2)
Net Earnings	118,376				118,376
Foreign Currency Translation Adjustment	935					935
Change in Net Unrealized Losses on Available-for-Sale Investments
Change in Net Unrealized Gains on Derivatives Designated as Cash Flow Hedges	12							12
Ending Balance at Dec. 31, 2010		(77,641)	45,376	201,752	809,084	922	(88)	12
Ending Balance (in shares) at Dec. 31, 2010		(10,665)
Dividends, $.049 and $.054 per share in 2010 and 2011 respectively					(4,152)
Stock-Based Compensation				8,385
Reissued Shares (in shares)		737
Reissued Shares		7,493		2,174
Repurchased Shares (in shares)		(5,184)
Repurchased Shares		(129,958)
Net Earnings	113,767				113,767
Foreign Currency Translation Adjustment	(648)					(648)
Change in Net Unrealized Losses on Available-for-Sale Investments							88
Change in Net Unrealized Gains on Derivatives Designated as Cash Flow Hedges	(12)							(12)
Ending Balance at Dec. 31, 2011	976,554	(200,106)	45,376	212,311	918,699	274
Ending Balance (in shares) at Dec. 31, 2011		(15,112)
Dividends, $.049 and $.054 per share in 2010 and 2011 respectively					(4,710)
Stock-Based Compensation				6,374
Reissued Shares (in shares)		1,317
Reissued Shares		17,662		1,677
Repurchased Shares (in shares)		(1,237)
Repurchased Shares		(34,131)
Net Earnings	173,043				173,043
Foreign Currency Translation Adjustment	30					(343)
Change in Net Unrealized Losses on Available-for-Sale Investments
Ending Balance at Dec. 31, 2012	$ 1,136,126	$ (216,575)	$ 45,376	$ 220,362	$ 1,087,032	$ (69)
Ending Balance (in shares) at Dec. 31, 2012		(15,032)