Segment And Geographic Information (Schedule Of Geographic Allocation Of Revenue) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenue	$ 81,567	$ 73,890	$ 69,443	$ 69,113	$ 73,521	$ 75,535	$ 74,286	$ 75,511	$ 294,013	$ 298,853	$ 284,924
Switzerland [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenue									54,023	50,118	50,805
Singapore [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenue									41,748	41,626	26,854
Korea [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenue									42,011	42,257	31,877
France [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenue									31,972	34,947	37,565
United States [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenue									4,756	6,648	7,253
Other Europe [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenue									57,893	63,141	54,677
Other Asia [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenue									58,283	58,349	67,695
Other International [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenue									$ 3,327	$ 1,767	$ 8,198