Income Taxes Income tax expense, income tax reconciliation (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
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									$ 37,173	$ 83,983	$ 81,026
Income Tax Reconciliation, Foreign Income Tax Rate Differential									(14,066)	(6,721)	(6,698)
Income Tax Reconciliation, Nondeductible Expense									2,832	2,807	2,138
Income Tax Reconciliation, Change in Deferred Tax Assets Valuation Allowance									3,625	1,150	(1,156)
Income Tax Reconciliation, State and Local Income Taxes									1,133	3,339	3,439
Income Tax Reconciliation, Prior Year Income Taxes									483	(2,973)	(4,258)
Income Tax Reconciliation, Other Adjustments									(1,205)	(1,570)	59
Income Tax Reconciliation, Other Reconciling Items									3,783	(2,710)	6,358
Income Tax Expense (Benefit)	$ 4,658	$ 9,753	$ 10,075	$ 9,272	$ 20,841	$ 19,909	$ 17,244	$ 19,311	$ 33,758	$ 77,305	$ 80,908