Employee Benefit Plans (Summary Of Stock Option Activity) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended	6 Months Ended
Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Options, Exercised (in shares)	(2,502)	(17,760)	(8,140)	(25,147)
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Roll Forward]
Proceeds from stock option exercises			$ 365	$ 968
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)			(8,140)	(25,147)
Options Outstanding, ending balance (in shares)	49,832	62,458	49,832	62,458
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)			44.85	38.51
Weighted-Average Exercise Price, Outstanding, ending balance (in dollars per share)	$ 52.18	$ 50.62	$ 52.18	$ 50.62
Exercisable (shares)	11,644	7,183	11,644	7,183
Exercisable, Weighted average exercise price (US$ per share)	$ 44.62	$ 44.32	$ 44.62	$ 44.32
Proceeds from stock option exercises			$ 365	$ 968
Intrinsic value of stock options exercised			263	824
Stock-based compensation expense associated with stock options			64	$ 95
Unrecognized stock-based compensation expense associated with stock options	$ 140		$ 140
Weighted average period (in years) in which the above amount is expected to be recognized			1 year 8 months 12 days

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

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