Other Current and Long-Term Assets (Schedule Of Other Long-term Assets) (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Other Assets, Noncurrent [Abstract]
Investment in long-term product supply arrangements	$ 11,621	$ 10,894
Customer acquisition costs	89,690	89,862
Contract assets	37,839	31,269
Deferred sales commissions	9,731	9,470
Deferred income taxes	8,368	8,481
Other assets	42,360	39,617
Other long-term assets	$ 199,609	$ 189,593