Income Taxes Income Tax Reconciliation (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income Tax Disclosure [Abstract]
Tax at the Netherlands income tax rate									$ 26,189	$ 25,427	$ 18,652
International earnings taxed at rates other than the Netherlands statutory rate									(14,997)	(12,496)	(16,840)
Non-deductible expenses									4,452	6,645	3,043
Change in valuation allowance									1,513	(1,744)	(899)
State and provincial taxes									1,566	829	600
Adjustments of prior year taxes									2,350	(4,272)	2,412
Adjustments of income tax reserves									(1,613)	1,869	(604)
Foreign exchange									5,936	(1,792)	3,381
Accrued withholding taxes									2,911	3,067	246
Other									(2,860)	716	864
Income tax expense	$ 5,750	$ 9,404	$ 5,020	$ 5,273	$ 8,016	$ 3,595	$ 3,709	$ 2,929	$ 25,447	$ 18,249	$ 10,855