Business Segment Information (Reconciliation Of Total Operating Profit Reported For Business Segments To Income From Operations In Consolidated Statements Of Operations) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Segment Reporting Information [Line Items]
Total operating profit from segments above	$ 460,778	$ 435,011	$ 412,664
Income from operations	396,944	375,694	358,213
Operating Segments [Member]
Segment Reporting Information [Line Items]
Total operating profit from segments above	460,778	435,011	412,664
Corporate, Non-Segment [Member]
Segment Reporting Information [Line Items]
Corporate overhead expenses	$ (63,834)	$ (59,317)	$ (54,451)