Consolidated Statement of Stockholders' Equity (USD $) In Thousands	Total	Common Stock	Additional Paid-In Capital	Retained Earnings	Treasury Stock	Accumulated Other Comprehensive Income (Loss)
Balance at Dec. 31, 2009	$ 1,247,514	$ 1,049	$ 686,592	$ 1,377,332	$ (819,754)	$ 2,295
Balance, shares at Dec. 31, 2009		104,911
Net earnings	171,642			171,642
Other comprehensive income (loss)	950					950
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	1,541,168	(904,274)	3,245
Balance, shares at Dec. 31, 2010		105,991
Net earnings	164,637			164,637
Other comprehensive income (loss)	(3,992)					(3,992)
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		1,077	757,933	1,669,389	(1,068,443)	(747)
Balance, shares at Dec. 31, 2011		107,800
Net earnings	183,492			183,492
Other comprehensive income (loss)	2,775					2,775
Purchase of treasury stock	(61,860)		(35)		(61,825)
Exercise of stock options	14,120	7	14,113
Exercise of stock options, shares		604
Vesting of restricted share units	1	1
Vesting of restricted share units, shares		127
Tax benefit related to stock option exercises	4,348		4,348
Stock-based compensation	8,366		8,366
Dividends	(40,588)			(40,588)
Balance at Dec. 31, 2012		$ 1,085	$ 784,725	$ 1,812,293	$ (1,130,268)	$ 2,028
Balance, shares at Dec. 31, 2012		108,531