Receivables (Schedule Of Trade Accounts Receivables Net) (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Accounts Receivable, Net, Current [Abstract]
Accounts receivable - trade	$ 231,187	$ 220,978
Allowance for doubtful accounts	(6,505)	(1,446)	$ (2,973)	$ (1,526)
Accounts receivable - trade, net	$ 224,682	$ 219,532