Stock-Based Compensation (Details Textual) (USD $)	12 Months Ended
Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Stock-Based Compensation (Textual) [Abstract]
Stock compensation expense	$ 3,469,000	$ 3,146,000	$ 3,628,000
Stock appreciation rights [Member]
Stock-Based Compensation (Textual) [Abstract]
Unrecognized compensation cost related to unvested awards	1,300,000
Recognized period for of cost of unvested awards	1 year 8 months 12 days
Maximum contractual term of Stock Appreciation Rights	10 years
Weighted-average fair value of grants	$ 25.75	$ 25.76	$ 17.94
Restricted stock [Member]
Stock-Based Compensation (Textual) [Abstract]
Stock compensation expense	2,000,000	1,600,000	1,700,000
Unrecognized compensation cost related to unvested awards	3,900,000
Recognized period for of cost of unvested awards	2 years 7 months 6 days
Restricted stock, Granted	156,927	67,945	91,845
Restricted shares were granted at per share	$ 27.18	$ 25.86	$ 17.41
Total fair value of restricted shares vested	2,500,000	4,100,000	2,700,000
Employee Stock Purchase Plan [Member]
Stock-Based Compensation (Textual) [Abstract]
Total aggregate number of shares of common stock that may be issued	300,000
Stock compensation expense	65,300	86,300	52,100
Percentage of market price on lesser of either first day of calendar quarter or last day of calendar quarter for purchase price	85.00%
Employees had purchased shares under the Employee Stock Purchase Plan	194,000
2005 Stock Incentive Plan [Member]
Stock-Based Compensation (Textual) [Abstract]
Number of stock based compensation plan	1
Total aggregate number of shares of common stock that may be issued	3,150,000
Stock compensation expense	$ 3,500,000	$ 3,100,000	$ 3,600,000
Minimum [Member] \| Employee Stock Purchase Plan [Member]
Stock-Based Compensation (Textual) [Abstract]
Percentage of gross compensation eligible employees may elect to participate in the plan	1.00%
Maximum [Member] \| Employee Stock Purchase Plan [Member]
Stock-Based Compensation (Textual) [Abstract]
Percentage of gross compensation eligible employees may elect to participate in the plan	15.00%

Number of shares employees purchased under employee stock purchase plan.

No definition available.

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- Definition

Number of stock based compensation plan.

+ References

No definition available.

+ Details

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- Definition

Share based compensation arrangement by share based payment award non options equity instruments granted weighted average grant price.

+ References

No definition available.

+ Details

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- Definition

Share based compensation arrangement by share based payment award Payroll deductions percentage.

+ References

No definition available.

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- Definition

Share based compensation arrangement by share based payment award terms of award maximum.

+ References

No definition available.

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- Definition

Weighted average period over which unrecognized compensation is expected to be recognized for equity-based compensation plans, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

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- Definition

Aggregate unrecognized cost of share-based awards, other than options, made to employees under an equity-based compensation plan, that have yet to vest.

+ References

No definition available.

+ Details

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- Definition

The aggregate amount of noncash, equity-based employee remuneration. This may include the value of stock or unit options, amortization of restricted stock or units, and adjustment for officers' compensation. As noncash, this element is an add back when calculating net cash generated by operating activities using the indirect method.

+ References

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 95

-Paragraph 28

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 45

-Paragraph 28

-Subparagraph (a)

-URI http://asc.fasb.org/extlink&oid=6943989&loc=d3e3602-108585

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- Definition

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).

+ References

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- Definition

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).

+ 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 (c)(2)(iii)(1)

-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 123R

-Paragraph A240

-Subparagraph c(1)

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 123R

-Paragraph A240

-Subparagraph b(2)(c)

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

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- Definition

The total fair value of equity-based awards 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.

+ References

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- Definition

The maximum number of shares (or other type of equity) originally approved (usually by shareholders and board of directors), net of any subsequent amendments and adjustments, for awards under the equity-based compensation plan. As stock or unit options and equity instruments other than options are awarded to participants, the shares or units remain authorized and become reserved for issuance under outstanding awards (not necessarily vested).

+ References

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 123R

-Paragraph A240

-Subparagraph a

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (a)(3)

-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

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- Definition

Purchase price of common stock expressed as a percentage of its fair market value.

+ References

No definition available.

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