Income Taxes Income tax expense, income tax reconciliation (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate									25.00%	25.00%	25.00%
Income Tax Reconciliation, Income Tax Expense (Benefit), at Federal Statutory Income Tax Rate									$ 83,983	$ 81,026	$ 72,115
Income Tax Reconciliation, Foreign Income Tax Rate Differential									(6,721)	(6,698)	(864)
Income Tax Reconciliation, Nondeductible Expense									2,807	2,138	917
Income Tax Reconciliation, Change in Deferred Tax Assets Valuation Allowance									1,150	(1,156)	(2,099)
Income Tax Reconciliation, State and Local Income Taxes									3,339	3,439	2,895
Income Tax Reconciliation, Prior Year Income Taxes									(2,973)	(4,258)	1,038
Income Tax Reconciliation, Other Adjustments									(1,570)	59	(4,374)
Income Tax Reconciliation, Other Reconciling Items									(2,710)	6,358	2,220
Income Tax Expense (Benefit)	$ 20,841	$ 19,909	$ 17,244	$ 19,311	$ 20,718	$ 20,490	$ 19,664	$ 20,036	$ 77,305	$ 80,908	$ 71,848