Employee Benefit Plans (Summary Of Stock Option Activity) (Details) - USD ($) $ / shares in Units, $ in Thousands	6 Months Ended
	Jun. 30, 2017	Jun. 30, 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)	(16,639)	(20,250)
Options, Forfeited (in shares)	0	0
Options Outstanding, ending balance (in shares)	87,605	99,113
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)	35.91	33.68
Weighted-Average Exercise Price, Forfeited (in dollars per share)	0.00	0.00
Weighted-Average Exercise Price, Outstanding, ending balance (in dollars per share)	$ 47.15	$ 40.68
Exercisable (shares)	7,887	15,500
Exercisable, Weighted average exercise price (US$ per share)	$ 37.37	$ 36.23
Proceeds from stock option exercises	$ 597	$ 682
Intrinsic value of stock options exercised	481	302
Stock-based compensation expense associated with stock options	125	$ 120
Unrecognized stock-based compensation expense associated with stock options	$ 503
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	2 years 10 months