Share-based Payment Arrangements (Schedule Of Information On Non-Vested Restricted Stock) (Details) (Non-Vested Restricted Stock [Member], USD $)	3 Months Ended
Mar. 31, 2012
Non-Vested Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Outstanding at December 31, 2011, Number of Shares	40,993
Outstanding at December 31, 2011, Weighted Average Grant Date Fair Value	$ 42.03
Vested, Number of Shares	(2,310)
Vested, Weighted Average Grant Date Fair Value	$ 39.10
Outstanding at March 31, 2012, Number of Shares	38,683
Outstanding at March 31, 2012, Weighted Average Grant Date Fair Value	$ 42.21

The number of non-vested equity-based payment instruments, excluding stock (or unit) options, that validly exist and are outstanding as of the balance sheet date.

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The weighted average fair value of nonvested awards on equity-based plans excluding option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, revenue or profit achievement stock award plan) for which the employer is contingently obligated to issue equity instruments or transfer assets to an employee who has not yet satisfied service or performance criteria necessary to gain title to proceeds from the sale of the award or underlying shares or units.

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- Definition

The weighted average fair value as of grant date pertaining to an equity-based award plan other than a stock (or unit) option plan for which the grantee gained the right during the reporting period, by satisfying service and performance requirements, to receive or retain shares or units, other instruments, or cash in accordance with the terms of the arrangement.

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