Employee Benefit Plans (Summary Of Stock Option Activity) (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Options
Options Outstanding, beginning balance	57,972	87,605	86,613
Options, Granted	0	0	17,631
Options, Exercised	(11,721)	(29,633)	(16,639)
Options, Forfeited	0	0	0
Options Outstanding, ending balance	46,251	57,972	87,605
Weighted-Average Exercise Price
Weighted-Average Exercise Price, Outstanding, beginning balance	$ 51.15	$ 47.15	$ 41.08
Weighted-Average Exercise Price, Granted	0	0	66.32
Weighted-Average Exercise Price, Exercised	44.87	39.31	35.91
Weighted-Average Exercise Price, Forfeited	0	0	0
Weighted-Average Exercise Price, Outstanding, ending balance	$ 52.74	$ 51.15	$ 47.15
Options, Exercisable at end of year	8,063	2,697	7,887
Weighted-Average Exercise Price, Exercisable at end of year	$ 44.48	$ 45.13	$ 37.37
Options
Share-based Compensation Arrangement by Share-based Payment Award, Options, Nonvested, Number of Shares	38,188	55,275	79,718	83,613
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Gross	0	0	17,631
Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested, Number of Shares	17,087	24,443	21,526
Share-based Compensation Arrangement by Share-based Payment Award, Options, Nonvested Options Forfeited, Number of Shares	0	0	0
Weighted-Average Exercise Price
Share-based Compensation Arrangement by Share-based Payment Award, Option, Nonvested, Weighted Average Exercise Price	$ 54.42	$ 51.40	$ 48.08	$ 41.47
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Weighted Average Grant Date Fair Value	0	0	66.32
Weighted-Average Exercise Price, Vested during the year	44.65	40.58	37.31
Weighted-Average Exercise Price, Forfeited during the year	$ 0	$ 0	$ 0
Proceeds from stock option exercises	$ 526	$ 1,164	$ 597
Intrinsic value of stock options exercised	368	944	481
Stock-based compensation expense associated with stock options	119	178	246
Income tax benefit recognized related to stock-based compensation	12	$ 19	$ 42
Unrecognized stock-based compensation expense	$ 84
Weighted average period in which the above amount is expected to be recognized	1 year 6 months