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Share-based Compensation (Details Textual) (USD $)	6 Months Ended
	Jun. 30, 2013 OptionPlan	Jun. 30, 2012
Share-Based Compensation (Additional Textual) [Abstract]
Number of inactive stock option plans	1
Number of active stock incentive plans	1
Unrecognized compensation expense	$ 5,700,000
Expected period of compensation expense recognition	2 years 1 month 6 days
Total intrinsic value	$ 117,000
Maximum duration over which RSUs and PSAs become exercisable under the plan	3 years
RSUs and PSAs at target level of performance included in unvested balance	198,000
Minimum Performance Awards issued multiplier	0.00%
Maximum Performance Awards issued multiplier	200.00%
Fair market value of stock option awards used in calculation of compensation expense, grant date	$ 27.49	$ 23.40
Director [Member]
Share-Based Compensation (Textual) [Abstract]
Stock awards granted to Non Employee Directors	4,912	4,807
Maximum [Member]
Share-Based Compensation (Textual) [Abstract]
Vesting period of PSAs	3 years
Minimum [Member]
Share-Based Compensation (Textual) [Abstract]
Vesting period of PSAs	2 years

X

- Definition

Weighted average period over which unrecognized compensation is expected to be recognized for equity-based compensation plans.

+ References

No definition available.

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- Definition

Maximum performance awards issued multiplier.

+ References

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- Definition

Minimum performance awards issued multiplier.

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- Definition

Number of active stock incentive plans.

+ References

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- Definition

Number of inactive stock option plans.

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X

- Definition

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

+ References

No definition available.

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X

- Definition

Period over which an employee's right to exercise a RSU is no longer contingent on satisfaction, in years.

+ References

No definition available.

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- Definition

Share based compensation arrangement by stock based payment award grant date fair value.

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- Definition

Unrecognized cost of unvested share-based awards, other than options, awarded to employees as compensation.

+ References

No definition available.

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- Definition

Period which an employee's right to exercise an award is no longer contingent on satisfaction of either a service condition, market condition or a performance condition, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (a)(1)

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- Definition

Amount of accumulated difference between fair value of underlying shares on dates of exercise and exercise price on options exercised (or share units converted) into shares.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

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-SubTopic 10

-Section 50

-Paragraph 2

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- Definition

The number of shares or units of entity securities issued in the transaction in which equity securities were issued to pay for goods or nonemployee services.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 505

-SubTopic 50

-Section 50

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=6406099&loc=d3e25284-112666



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