Other Current and Long-Term Assets (Schedule Of Other Long-term Assets) (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Other Current and Long-Term Assets [Abstract]
Investment in long-term product supply arrangements	$ 10,324	$ 9,949
Customer acquisition costs (Notes 2 and 3)	83,417	64,670
Contract assets (Notes 2 and 3)	7,202
Deferred sales commissions (Notes 2 and 3)	8,013
Deferred income taxes (Note 2)	9,823	7,698
Other assets (Notes 2 and 3)	21,845	36,299
Other long-term assets	$ 140,624	$ 118,616