Income Taxes (Details 1) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2010	Sep. 30, 2010	Jun. 30, 2010	Mar. 31, 2010	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Components of income tax expense
Federal current									$ 47,993	$ 113,837	$ 125,126
Federal deferred									21,075	(3,218)	5,704
Total federal									69,068	110,619	130,830
State current									2,203	1,797	3,001
State deferred									2,489	1,891	2,511
Total state									4,692	3,688	5,512
Foreign current									28,543	31,691	27,996
Foreign deferred									(2,790)	317	2,137
Total foreign									25,753	32,008	30,133
Uncertain tax positions									250	(1,584)	(1,792)
Income tax expense	$ 34,092	$ 22,355	$ 27,427	$ 15,889	$ 37,738	$ 38,949	$ 36,373	$ 31,671	$ 99,763	$ 144,731	$ 164,683