Consolidated Statements of Stockholders' Equity (USD $) In Thousands, unless otherwise specified	Common Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]	Treasury Stock [Member]	Total
Balances at Dec. 31, 2009	$ 1,671	$ 176,009	$ 1,423,820	$ (957,647)	$ 643,853
Comprehensive income:
Net earnings			199,617		199,617
Cash dividend declared and paid			(59,910)		(59,910)
Tax benefit of stock options exercised		12,154			12,154
Purchase of treasury shares				(250,892)	(250,892)
Stock compensation		21,397			21,397
Stock option exercises and restricted share issuances, net of stock repurchased for payroll taxes		(28,574)		35,376	6,802
Balances at Dec. 31, 2010	1,671	180,986	1,563,527	(1,173,163)	573,021
Comprehensive income:
Net earnings			257,006		257,006
Cash dividend declared and paid			(62,243)		(62,243)
Tax benefit of stock options exercised		15,562			15,562
Purchase of treasury shares				(246,406)	(246,406)
Stock compensation		26,841			26,841
Stock option exercises and restricted share issuances, net of stock repurchased for payroll taxes		(30,919)		34,681	3,762
Balances at Dec. 31, 2011	1,671	192,470	1,758,290	(1,384,888)	567,543
Comprehensive income:
Net earnings			310,354		310,354
Cash dividend declared and paid			(83,431)		(83,431)
Tax benefit of stock options exercised		20,090			20,090
Purchase of treasury shares				(50,000)	(50,000)
Stock compensation		29,715			29,715
Stock option exercises and restricted share issuances, net of stock repurchased for payroll taxes		(35,202)		32,791	(2,411)
Balances at Dec. 31, 2012	$ 1,671	$ 207,073	$ 1,985,213	$ (1,402,097)	$ 791,860