Segment And Geographic Information (Schedule Of Geographic Allocation Of Revenue) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Total revenue	$ 65,692	$ 66,117	$ 59,366	$ 58,492	$ 58,810	$ 59,203	$ 55,312	$ 54,264	$ 249,667	$ 227,589	$ 212,405
United States [Member]
Total revenue									48,103	13,821	11,605
France [Member]
Total revenue									25,811	26,586	23,956
Japan [Member]
Total revenue									24,919	26,124	24,353
Switzerland [Member]
Total revenue									18,937	22,813	21,727
Korea [Member]
Total revenue									17,703	23,169	22,781
Other Asia [Member]
Total revenue									62,702	64,677	57,421
Other Europe [Member]
Total revenue									37,353	33,235	31,493
Other International [Member]
Total revenue									$ 14,139	$ 17,164	$ 19,069