Income Taxes Income tax expense, income tax reconciliation (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Current Fiscal Year End Date									--12-31
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate									25.00%	25.00%	25.50%
Income Tax Reconciliation, Income Tax Expense (Benefit), at Federal Statutory Income Tax Rate									$ 72,115	$ 59,711	$ 53,333
Income Tax Reconciliation, Foreign Income Tax Rate Differential									(864)	(241)	3,698
Income Tax Reconciliation, Nondeductible Expense									917	2,691	2,524
Income Tax Reconciliation, Change in Deferred Tax Assets Valuation Allowance									(2,099)	(1,279)	75
Income Tax Reconciliation, State and Local Income Taxes									2,895	3,166	2,597
Income Tax Reconciliation, Prior Year Income Taxes									1,038	(17,229)	(389)
Income Tax Reconciliation, Other Adjustments									(4,374)	7,050	4,093
Income Tax Reconciliation, Other Reconciling Items									2,220	329	(2,184)
Income Tax Expense (Benefit)	18,394	18,671	16,997	17,786	17,371	14,599	14,710	7,518	71,848	54,198	63,747
Income Tax Reconciliation, Tax Settlements										$ 10,400