Employee Benefit Plans (Summary Of Stock Option Activity) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
Mar. 31, 2019	Mar. 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Options, Exercised (in shares)	(5,638)	(7,388)
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Roll Forward]
Proceeds from stock option exercises	$ 252	$ 280
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)	(5,638)	(7,387)
Options Outstanding, ending balance (in shares)	52,334	80,218
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)	44.74	37.85
Weighted-Average Exercise Price, Outstanding, ending balance (in dollars per share)	$ 51.84	$ 48.00
Exercisable (shares)	14,146	24,943
Exercisable, Weighted average exercise price (US$ per share)	$ 44.70	$ 40.38
Proceeds from stock option exercises	$ 252	$ 280
Intrinsic value of stock options exercised	177	220
Stock-based compensation expense associated with stock options	37	$ 54
Unrecognized stock-based compensation expense associated with stock options	$ 167
Weighted average period (in years) in which the above amount is expected to be recognized	1 year 11 months

Represents the expense recognized during the period arising from equity-based compensation arrangements (for example, shares of stock, unit, stock options or other equity instruments) with employees, directors and certain consultants qualifying for treatment as employees.

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Weighted average period over which unrecognized compensation is expected to be recognized for equity-based compensation plans, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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Unrecognized cost of unvested options awarded to employees as compensation.

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Amount of cash inflow from exercise of stock options granted under share-based compensation arrangement.

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The number of shares into which fully or partially vested stock options outstanding as of the balance sheet date can be currently converted under the option plan.

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Weighted average price at which option holders acquired shares when converting their stock options into shares.

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The number of shares reserved for issuance pertaining to the outstanding stock options as of the balance sheet date for all option plans in the customized range of exercise prices.

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Weighted average exercise price as of the balance sheet date for those equity-based payment arrangements exercisable and outstanding.

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