Income Taxes (Narrative) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate		35.00%	35.00%	35.00%
Effective Income Tax Rate Reconciliation, Nondeductible Expense, Share-based Compensation Cost, Percent		6.70%
Effective Income Tax Rate Reconciliation, Tax Credit, Foreign, Percent		1.00%
Effective Income Tax Rate Reconciliation, Repatriation of Foreign Earnings, Percent		9.40%
Impact t of tax reform on deferred taxes		8.00%
Effective Tax Rate		30.90%	31.00%	29.70%
Income taxes paid		$ 81,200	$ 74,700	$ 54,900
Income tax ruling exemption		8,900	7,800	8,500
Unrecognized tax benefits		21,417	18,463	7,204	$ 5,942
Unrecognized tax benefits that would impact effective tax rate if recognized		9,100	5,900
Decrease to net deferred tax liabilities		17,000
Deferred Tax Assets, Valuation Allowance		6,211	4,891
Interest expense and penalties related to unrecognized tax benefits		900	300	$ 300
Interest expense and penalties accrued		1,000	$ 600
Net operating loss carryforwards in certain state and international jurisdictions		13,100
Recognized Provisional Amount, Net, Transition Tax Liability		$ 48,800
Scenario, Forecast [Member]
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate	21.00%
Repatriation Tax, Previously Tax Deferred, Payable Term	8 years
Netherlands [Member]
Expiration date for tax holidays		December 31, 2022,
Accounting Standards Update 2016-09 [Member]
Effective Income Tax Rate Reconciliation, Nondeductible Expense, Share-based Compensation Cost, Percent		7.00%