Employee Benefit Plans (Summary Of Stock Option Activity) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended	9 Months Ended
Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Options, Exercised (in shares)	(3,581)	(3,986)	(11,721)	(29,133)
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Roll Forward]
Proceeds from stock option exercises			$ 526	$ 1,149
Employee Stock Option
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Options Outstanding, beginning balance (in shares)			57,972	87,605
Options, Exercised (in shares)			(11,721)	(29,133)
Options Outstanding, ending balance (in shares)	46,251	58,472	46,251	58,472
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)			$ 51.15	$ 47.15
Weighted-Average Exercise Price, Exercised (in dollars per share)			44.87	39.47
Weighted-Average Exercise Price, Outstanding, ending balance (in dollars per share)	$ 52.74	$ 50.97	$ 52.74	$ 50.97
Exercisable (shares)	8,063	3,197	8,063	3,197
Exercisable, Weighted average exercise price (US$ per share)	$ 44.48	$ 42.82	$ 44.48	$ 42.82
Proceeds from stock option exercises			$ 526	$ 1,149
Intrinsic value of stock options exercised			368	944
Stock-based compensation expense associated with stock options			92	$ 137
Unrecognized stock-based compensation expense associated with stock options	$ 112		$ 112
Weighted average period (in years) in which the above amount is expected to be recognized			1 year 7 months 6 days

Amount of expense for award under share-based payment arrangement. Excludes amount capitalized.

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