Segment Reporting (Schedule Of Net Long-Lived Assets By Principal Geographic Areas) (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Revenues from External Customers and Long-Lived Assets [Line Items]
Net Assets	$ 379,096	$ 357,422
Americas [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Net Assets	329,964	318,831
Americas [Member] | United States [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Net Assets	310,696	298,944
Americas [Member] | Brazil [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Net Assets	17,030	17,910
Americas [Member] | Canada [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Net Assets	2,238	1,977
Europe, The Middle East And Africa [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Net Assets	35,173	28,483
Europe, The Middle East And Africa [Member] | United Kingdom [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Net Assets	11,528	9,127
Europe, The Middle East And Africa [Member] | Germany [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Net Assets	7,522	5,040
Europe, The Middle East And Africa [Member] | Netherlands [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Net Assets	8,225	5,948
Europe, The Middle East And Africa [Member] | France [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Net Assets	2,305	2,428
Europe, The Middle East And Africa [Member] | Switzerland [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Net Assets	1,755	2,450
Europe, The Middle East And Africa [Member] | Other Europe [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Net Assets	3,838	3,490
Asia Pacific Region [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Net Assets	13,959	10,108
Asia Pacific Region [Member] | Japan [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Net Assets	4,065	2,469
Asia Pacific Region [Member] | Australia [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Net Assets	4,426	4,185
Asia Pacific Region [Member] | Other Asia Pacific [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Net Assets	$ 5,468	$ 3,454