Receivables (Schedule Of Allowance For Doubtful Accounts) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Allowance for Doubtful Accounts Receivable [Roll Forward]
Balance at beginning of period	$ 1,446	$ 2,973	$ 1,526
Charged to costs and expenses	6,463	1,242	1,447
Amounts written off	(1,404)	(2,769)	0
Balance at end of period	$ 6,505	$ 1,446	$ 2,973