Other Current and Long-Term Assets (Schedule Of Other Long-term Assets) (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Jan. 01, 2018	Dec. 31, 2017
Other Assets, Noncurrent [Abstract]
Investment in long-term product supply arrangements	$ 10,532		$ 9,949
Customer acquisition costs (Notes 2 and 3)	87,034		64,670
Contract assets (Notes 2 and 3)	21,680		0
Deferred sales commissions (Notes 2 and 3)	8,894	$ 11,800	0
Deferred income taxes (Note 2)	8,436		7,698
Other assets (Notes 2 and 3)	35,311		36,299
Other long-term assets	$ 171,887		$ 118,616