Fixed Assets (Schedule Of Fixed Assets) (Details) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016	Jun. 30, 2016
Property, Plant and Equipment [Abstract]
Fixed assets, at cost	$ 381,650	$ 337,362	$ 304,982
Less accumulated depreciation and amortization	178,446	164,614	153,732
Fixed assets, net	$ 203,204	$ 172,748	$ 151,250