Income Taxes Income tax expense, income tax reconciliation (Details) (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
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate									25.00%	25.50%	25.50%
Income Tax Reconciliation, Income Tax Expense (Benefit), at Federal Statutory Income Tax Rate									$ 59,711	$ 53,333	$ 43,671
Income Tax Reconciliation, Reserve for Pending Audit Settlements									0	0	(4,468)
Income Tax Reconciliation, Foreign Income Tax Rate Differential									(241)	3,698	8,618
Income Tax Reconciliation, Nondeductible Expense									2,691	2,524	3,366
Income Tax Reconciliation, Change in Deferred Tax Assets Valuation Allowance									(1,279)	75	1,564
Income Tax Reconciliation, State and Local Income Taxes									3,166	2,597	3,954
Income Tax Reconciliation, Prior Year Income Taxes									(17,229)	(389)	(297)
Income Tax Reconciliation, Other Adjustments									7,050	4,093	3,402
Income Tax Reconciliation, Other Reconciling Items									329	(2,184)	(2,646)
Income Tax Expense (Benefit)	17,371	14,599	14,710	7,518	16,671	16,764	15,244	15,068	54,198	63,747	57,164
Income Tax Reconciliation, Tax Settlements									$ 10,400