Accrued And Other Liabilities (Schedule Of Recognized Warranty Revenue And Incurred Warranty Costs) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Accrued And Other Liabilities [Abstract]
Beginning Balance Deferred Warranty Revenue	$ 9,051	$ 10,663	$ 11,914
Warranty Revenue Deferred	13,623	12,859	15,349
Warranty Revenue Recognized	(12,472)	(14,471)	(16,600)
Ending Balance Deferred Warranty Revenue	$ 10,202	$ 9,051	$ 10,663