Consolidated Statement of Stockholders' Equity (USD $) In Thousands, unless otherwise specified	Total	Common Stock	Additional Paid-In Capital	Retained Earnings	Treasury Stock
Balance at Dec. 31, 2008	$ 1,079,202	$ 1,047	$ 681,067	$ 1,208,009	$ (810,921)
Balance, shares at Dec. 31, 2008		104,769
Net earnings	167,855			167,855
Other comprehensive income:
Foreign currency translation adjustment	2,295			2,295
Comprehensive income	170,150
Purchase of treasury stock	(8,846)		(13)		(8,833)
Exercise of stock options	1,537	2	1,535
Exercise of stock options, shares		142
Tax benefit related to stock option exercises	270		270
Stock-based compensation	3,731		3,731
Other	1,470		2	1,468
Balance at Dec. 31, 2009	1,247,514	1,049	686,592	1,379,627	(819,754)
Balance, shares at Dec. 31, 2009		104,911
Net earnings	171,642			171,642
Other comprehensive income:
Foreign currency translation adjustment	950			950
Comprehensive income	172,592
Purchase of treasury stock	(84,592)		(72)		(84,520)
Exercise of stock options	19,040	11	19,029
Exercise of stock options, shares		1,080
Tax benefit related to stock option exercises	2,974		2,974
Stock-based compensation	4,123		4,123
Dividends	(7,804)			(7,804)
Other	(48)		(46)	(2)
Balance at Dec. 31, 2010	1,353,799	1,060	712,600	1,544,413	(904,274)
Balance, shares at Dec. 31, 2010		105,991
Net earnings	164,637			164,637
Other comprehensive income:
Foreign currency translation adjustment	(3,992)			(3,992)
Comprehensive income	160,645
Purchase of treasury stock	(164,285)		(116)		(164,169)
Exercise of stock options	34,910	17	34,893
Exercise of stock options, shares		1,809
Tax benefit related to stock option exercises	7,036		7,036
Stock-based compensation	4,471		4,471
Dividends	(36,357)			(36,357)
Other	(1,010)		(951)	(59)
Balance at Dec. 31, 2011	$ 1,359,209	$ 1,077	$ 757,933	$ 1,668,642	$ (1,068,443)
Balance, shares at Dec. 31, 2011		107,800