Acquisitions (Schedule Of Business Acquisitions Pro Forma Of Operations) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Acquisitions [Abstract]
Service revenues and sales	$ 528,297	$ 500,289	$ 1,546,674	$ 1,480,432
Net income	$ 67,722	$ 62,194	$ 205,773	$ 164,679
Earnings per share	$ 4.25	$ 3.89	$ 12.90	$ 10.32
Diluted earnings per share	$ 4.14	$ 3.76	$ 12.53	$ 9.97