Employee Benefit Plans (Summary Of Stock Option Activity) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Options, Exercised (in shares)	(3,686)	0	(29,133)	(16,639)
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Roll Forward]
Proceeds from stock option exercises			$ 1,149	$ 597
Employee Stock Option
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Options Outstanding, beginning balance (in shares)			87,605	86,613
Options, Granted (in shares)			0	17,631
Options, Exercised (in shares)			(29,133)	(16,639)
Options Outstanding, ending balance (in shares)	58,472	87,605	58,472	87,605
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)			$ 47.15	$ 41.08
Weighted-Average Exercise Price, Granted (in dollars per share)			0.00	66.32
Weighted-Average Exercise Price, Exercised (in dollars per share)			39.47	35.91
Weighted-Average Exercise Price, Outstanding, ending balance (in dollars per share)	$ 50.97	$ 47.15	$ 50.97	$ 47.15
Exercisable (shares)	3,197	7,887	3,197	7,887
Exercisable, Weighted average exercise price (US$ per share)	$ 42.82	$ 37.37	$ 42.82	$ 37.37
Proceeds from stock option exercises			$ 1,149	$ 597
Intrinsic value of stock options exercised			944	481
Stock-based compensation expense associated with stock options			137	$ 186
Unrecognized stock-based compensation expense associated with stock options	$ 245		$ 245
Weighted average period (in years) in which the above amount is expected to be recognized			2 years 1 month