Share-Based Compensation 2 (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	9 Months Ended
Sep. 30, 2012
Summary of the status of non vested share grants [Roll Forward]
Beginning balance nonvested	623
Granted	380
Vested	(294)
Forfeited	(23)
Ending balance nonvested	686
Weighted-Average Grant-Date Fair Value and Aggregate Instrinsic Value [Roll Forward]
Beginning balance nonvested	$ 22.91
Granted	$ 18.82
Vested	$ 21.71
Forfeited	$ 22.07
Ending balance nonvested	$ 21.19
Beginning balance nonvested	$ 14,279,000
Vested	$ 6,373,000
Ending balance nonvested	$ 14,529,000
Share-based Compensation Arrangement by Share-based Payment Award, Award Requisite Service Period	Stock Options. Stock options generally vest in equal annual installments over a four-year period and expire ten years after the grant date, Share Grants. Restricted stock awards and restricted stock units generally vest in equal annual installments over a four-year period.
Share-based Compensation Arrangement by Share-based Payment Award, Method of Measuring Cost of Award	expense was estimated on the date of grant using the Black-Scholes-Merton option pricing model.

Description of the estimated period of time over which an employee is required to provide service in exchange for the equity-based payment award, which often is the vesting period. This period may be explicit or implicit based on the terms of the award, and may be presented in a variety of ways (for example, year, month and year, day, month and year, quarter of a year).

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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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The 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 during the reporting period as a result of the occurrence of a terminating event specified in the contractual agreement of the plan.

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

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The intrinsic value of equity-based payment equity instruments, excluding stock (or unit) options, that vested during the reporting period as calculated by applying the disclosed pricing methodology.

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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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Description of the method used for calculating compensation cost for the award under the plan.

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