Employee Benefit Plans (Summary Of Stock Option Activity) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Options Outstanding, beginning balance (in shares)	86,613	95,015
Options, Granted (in shares)	17,631	24,348
Options, Exercised (in shares)	(1,250)	0
Options, Forfeited (in shares)	0	0
Options Outstanding, ending balance (in shares)	102,994	119,363
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Roll Forward]
Weighted-Average Exercise Price, Outstanding, beginning balance (in dollars per share)	$ 41.08	$ 38.38
Weighted-Average Exercise Price, Granted (in dollars per share)	66.32	43.73
Weighted-Average Exercise Price, Exercised (in dollars per share)	30.38	0.00
Weighted-Average Exercise Price, Forfeited (in dollars per share)	0.00	0.00
Weighted-Average Exercise Price, Outstanding, ending balance (in dollars per share)	$ 45.53	$ 39.49
Exercisable (shares)	23,276	35,750
Exercisable, Weighted average exercise price (US$ per share)	$ 36.70	$ 34.79
Proceeds from stock option exercises	$ 38	$ 0
Intrinsic value of stock options exercised	44	0
Stock-based compensation expense associated with stock options	65	$ 60
Unrecognized stock-based compensation expense associated with stock options	$ 563
Employee Stock Option [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Roll Forward]
Weighted average period (in years) in which the above amount is expected to be recognized	3 years