Earnings Per Share (Schedule Of Computation Of Earnings Per Share) (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Earnings Per Share[Abstract]
Earnings	$ 50,729	$ 54,971	$ 95,396	$ 99,967
Diluted Earnings	$ 50,729	$ 54,971	$ 95,396	$ 99,967
Earnings, Shares	15,928	16,035	15,941	16,067
Dilutive stock options, Shares	449	674	474	683
Nonvested stock awards, Shares	72	102	74	104
Diluted Earnings, Shares	16,449	16,811	16,489	16,854
Earnings per Share, Earnings	$ 3.18	$ 3.43	$ 5.98	$ 6.22
Earnings per Share, Diluted earnings	$ 3.08	$ 3.27	$ 5.79	$ 5.93