Employee Benefit Plans (Summary Of Stock Option Activity) (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Options
Options Outstanding, beginning balance	87,605	86,613	95,015
Options, Granted	0	17,631	24,348
Options, Exercised	(29,633)	(16,639)	(32,750)
Options, Forfeited	0	0	0
Options Outstanding, ending balance	57,972	87,605	86,613
Weighted-Average Exercise Price
Weighted-Average Exercise Price, Outstanding, beginning balance	$ 47.15	$ 41.08	$ 38.38
Weighted-Average Exercise Price, Granted	0.00	66.32	43.73
Weighted-Average Exercise Price, Exercised	(39.31)	(35.91)	(35.28)
Weighted-Average Exercise Price, Forfeited	0.00	0.00	0.00
Weighted-Average Exercise Price, Outstanding, ending balance	$ 51.15	$ 47.15	$ 41.08
Options, Exercisable at end of year	2,697	7,887	3,000
Weighted-Average Exercise Price, Exercisable at end of year	$ 45.13	$ 37.37	$ 29.45
Options
Share-based Compensation Arrangement by Share-based Payment Award, Options, Nonvested, Number of Shares	55,275	79,718	83,613	75,265
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Gross	0	17,631	24,348
Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested, Number of Shares	24,443	21,526	16,000
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	$ 51.40	$ 48.08	$ 41.47	$ 39.38
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Weighted Average Grant Date Fair Value	0.00	66.32	43.73
Weighted-Average Exercise Price, Vested during the year	40.58	37.31	35.09
Weighted-Average Exercise Price, Forfeited during the year	$ 0.00	$ 0.00	$ 0
Proceeds from stock option exercises	$ 1,164	$ 597	$ 1,155
Intrinsic value of stock options exercised	944	481	551
Stock-based compensation expense associated with stock options	178	246	240
Income tax benefit recognized related to stock-based compensation	19	$ 42	$ 36
Unrecognized stock-based compensation expense	$ 204
Weighted average period in which the above amount is expected to be recognized	2 years