Fixed Assets (Schedule Of Fixed Assets) (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016	Sep. 30, 2016
Property, Plant and Equipment [Abstract]
Fixed assets, at cost	$ 396,789	$ 337,362	$ 313,057
Less accumulated depreciation and amortization	186,485	164,614	159,890
Fixed assets, net	$ 210,304	$ 172,748	$ 153,167