Computation Of Basic And Diluted Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Earnings Per Share [Abstract]
Net income	$ 15,301	$ 7,952	$ 22,785	$ 20,078
Weighted average common shares outstanding - Basic	1,892	1,889	1,892	1,888
Incremental shares outstanding assuming the exercise of dilutive stock options and SARs (share settled)	3	6	4	8
Weighted average common shares outstanding - Diluted	1,895	1,895	1,896	1,896
Basic Earnings per Common Share	$ 8.09	$ 4.21	$ 12.04	$ 10.63
Diluted Earnings per Common Share	$ 8.07	$ 4.20	$ 12.02	$ 10.59