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Share-Based Compensation (Details2) (Restricted Stock Units and Performance Awards [Member], USD $)	6 Months Ended
	Jun. 30, 2012
Restricted Stock Units and Performance Awards [Member]
Summary of the status of the Company's restricted stock units and performance awards
Number of unvested Restricted Stock Units and Performance Awards at January 1, 2012	193,981
Number of Restricted Stock Units and Performance Awards granted	115,306
Number of Restricted Stock Units and Performance Awards vested	(20,840)
Number of Restricted Stock Units and Performance Awards cancelled	(35,215)
Number of unvested Restricted Stock Units and Performance Awards at June 30, 2012	253,232
Weighted Average Grant Date Fair Value, Unvested restricted stock units and performance awards at January 1, 2012	$ 24.41
Weighted Average Grant Date Fair Value, Restricted stock units and performance awards granted	$ 29.06
Weighted Average Grant Date Fair Value, Restricted stock units and performance awards vested	$ 22.95
Weighted Average Grant Date Fair Value, Restricted stock units and performance awards granted	$ 29.02
Weighted Average Grant Date Fair Value, Unvested restricted stock units and performance awards at June 30, 2012	$ 26.01

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The number of equity-based payment instruments, excluding stock (or unit) options, that were forfeited during the reporting period.

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Weighted average fair value as of the grant date of equity-based award plans other than stock (unit) option plans that were not exercised or put into effect as a result of the occurrence of a terminating event.

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The number of grants made 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 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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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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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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