Stock Benefit Plan (Summary Of Restricted Stock Activity) (Details) (Restricted Stock [Member], USD $)	12 Months Ended
Dec. 31, 2011
Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restricted stock outstanding and unvested, Number of Shares, Beginning Balance	283,215
Restricted stock outstanding and unvested, Weighted Average Grant Date Fair Value Per Share, Beginning Balance	$ 44.58
Granted, Number of Shares	97,377
Granted, Weighted Average Grant Date Fair Value Per Share	$ 62.09
Vested and issued, Number of Shares	(85,327)
Vested and issued, Weighted Average Grant Date Fair Value Per Share	$ 45.26
Cancelled, Number of Shares	(5,817)
Cancelled, Weighted Average Grant Date Fair Value Per Share	$ 43.64
Restricted stock outstanding and unvested, Number of Shares, Ending Balance	289,448
Restricted stock outstanding and unvested, Weighted Average Grant Date Fair Value Per Share	$ 50.29

The weighted average fair value at grant date for nonvested equity-based awards issued during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

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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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- Definition

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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