Receivables (Schedule Of Trade Accounts Receivables Net) (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Accounts Receivable, Net, Current [Abstract]
Accounts receivable - trade	$ 220,978	$ 274,502
Allowance for doubtful accounts	(1,446)	(2,973)	$ (1,526)	$ (2,372)
Accounts receivable - trade, net	$ 219,532	$ 271,529