Earnings Per Share (Schedule Of Computation Of Earnings Per Share) (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Earnings Per Share[Abstract]
Earnings	$ 58,947	$ 51,249	$ 154,343	$ 151,216
Diluted earnings	$ 58,947	$ 51,249	$ 154,343	$ 151,216
Earnings, Shares	15,970	16,074	15,952	16,070
Dilutive stock options, Shares	500	613	484	662
Nonvested stock awards, Shares	85	85	78	98
Diluted earnings, Shares	16,555	16,772	16,514	16,830
Earnings, Earnings per Share	$ 3.69	$ 3.19	$ 9.68	$ 9.41
Diluted earnings, Earnings per Share	$ 3.56	$ 3.06	$ 9.35	$ 8.98