Consolidated Statements Of Stockholders' Equity and Comprehensive Income (USD $) In Thousands, except Share data	Common Stock [Member]	Additional Paid-In Capital [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Total
Balance at Dec. 31, 2008	$ 2,970	$ 74	$ 1,134,244	$ 4,971	$ 1,142,259
Balance (in shares) at Dec. 31, 2008	297,061,000
Dividends paid in cash	0	0	(106,943)	0	(106,943)
Purchase of common stock	(22)	(5,065)	(36,017)	0	(41,104)
Purchase of common stock (in shares)	(2,200,000)
Stock options expense	0	3,850	0	0	3,850
Net earnings for the year	0	0	184,357	0	184,357
Change in marketable securities	0	0	0	5	5
Translation adjustment (net of tax effect)	0	0	0	8,419	8,419
Total comprehensive income					192,781
Balance at Dec. 31, 2009	2,948	(1,141)	1,175,641	13,395	1,190,843
Balance (in shares) at Dec. 31, 2009	294,861,000
Dividends paid in cash	0	0	(182,814)	0	(182,814)
Purchase of common stock	0	0	0	0	0
Purchase of common stock (in shares)	0
Stock options expense	0	4,030	0	0	4,030
Net earnings for the year	0	0	265,356	0	265,356
Change in marketable securities	0	0	0	35	35
Translation adjustment (net of tax effect)	0	0	0	5,062	5,062
Total comprehensive income					270,453
Balance at Dec. 31, 2010	2,948	2,889	1,258,183	18,492	1,282,512
Balance (in shares) at Dec. 31, 2010	294,861,000
Dividends paid in cash	0	0	(191,741)	0	(191,741)
Purchase of common stock	0	0	0	0	0
Purchase of common stock (in shares)	0
Stock options exercised	5	8,934	0	0	8,939
Stock options exercised (in shares)	397,000
Stock options expense	0	4,050	0	0	4,050
Tax benefit from exercise of stock options	0	983	0	0	983
Net earnings for the year	0	0	357,929	0	357,929
Change in marketable securities	0	0	0	95	95
Translation adjustment (net of tax effect)	0	0	0	(3,791)	(3,791)
Total comprehensive income					354,233
Balance at Dec. 31, 2011	$ 2,953	$ 16,856	$ 1,424,371	$ 14,796	$ 1,458,976
Balance (in shares) at Dec. 31, 2011	295,258,000