Equity-Based Compensation (Summary Of Outstanding Performance Share Awards) (Details) (Performance Shares [Member], USD $)	6 Months Ended	12 Months Ended
Jun. 30, 2011	Dec. 31, 2010
Performance Shares [Member]
Unvested shares outstanding at January 1, Shares	184,601
Granted, Shares	77,767	81,162
Forfeited, Shares	(809)
Unvested shares outstanding at June 30, Shares	261,559	184,601
Unvested shares outstanding at January 1, Weighted Avg. Grant Date Fair Value	$ 38.45
Granted, Weighted Avg. Grant Date Fair Value	$ 55.84	$ 45.30
Forfeited, Weighted Avg. Grant Date Fair Value	$ 41.48
Unvested shares outstanding at June 30, Weighted Avg. Grant Date Fair Value	$ 43.61	$ 38.45
Unvested shares outstanding at June 30, Aggregate Intrinsic Value	$ 8,866.000

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 intrinsic 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, as calculated by applying the disclosed pricing methodology.

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- Definition

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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