Accrued Liabilities (Schedule Of Accrued Liabilities) (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Accrued Liabilities, Current [Abstract]
Accrued expenses	$ 61,302	$ 64,430
Accrued employee compensation and related expenses	79,394	102,944
Accrued taxes	25,109	29,389
Accrued customer incentives and refund obligations (Notes 2 and 3)	62,575	56,655
Total accrued liabilities	$ 228,380	$ 253,418