Segment And Geographic Information (Schedule Of Geographic Allocation Of Revenue) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenue	$ 94,034	$ 90,161	$ 82,692	$ 81,506	$ 77,274	$ 78,472	$ 71,642	$ 66,966	$ 348,393	$ 294,354	$ 249,667
United States [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenue									120,558	99,824	36,197
France [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenue									34,862	29,273	27,603
Switzerland [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenue									32,430	19,636	20,215
Korea [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenue									20,755	14,904	18,933
Japan [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenue									20,388	21,717	26,559
Singapore [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenue									19,856	16,172	18,627
Other Europe [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenue									45,176	40,170	41,034
Other Asia [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenue									43,709	41,473	47,301
Other International [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenue									$ 10,659	$ 11,185	$ 13,198