Employee Benefit Plans (Details Textual) (USD $) In Thousands, unless otherwise specified	12 Months Ended
Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Defined Benefit Plan Disclosure [Line Items]
Percentage of contribution	3.00%
Employee Benefit Plans (Textual) [Abstract]
Contribution to defined benefit pension plan	$ 1,693
Accumulated benefit obligation for defined benefit pension plan	49,301	40,949
Accumulated benefit obligation for supplementary pension plan	8,537	7,606
Amount expected to be amortized in the next fiscal year for the unrecognized prior service cost	59
Amount expected to be amortized in the next fiscal year for the unrecognized net actuarial loss	1,153
Target allocation minimum percentage in equity securities	41.00%
Target allocation maximum percentage in equity securities	69.00%
Target allocation minimum percentage in fixed income securities and bonds	18.00%
Target allocation maximum percentage in fixed income securities and bonds	31.00%
Target allocation minimum percentage in alternative investments	5.00%
Target allocation maximum percentage in alternative investments	23.00%
Target allocation minimum percentage in cash	0.00%
Target allocation maximum percentage in cash	10.00%
Evaluation of investment allocations	at least twice a year by the Pension Committee
Company contribution	1,778	1,248	1,021
401(k) Savings Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Percentage of contribution	4.00%
Company contribution	$ 3,422	$ 2,842	$ 2,803

Target allocation maximum percentage in cash.

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Target allocation minimum percentage in cash.

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No definition available.

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Investment allocations being evaluated.

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Percentage of contribution.

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No definition available.

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- Definition

Supplementary pension plan, accumulated benefit obligation.

+ References

No definition available.

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For defined benefit pension plans, the actuarial present value of benefits (whether vested or nonvested) attributed by the pension benefit formula to employee service rendered before a specified date and based on employee service and compensation (if applicable) before that date. The accumulated benefit obligation differs from the projected benefit obligation in that it includes no assumption about future compensation levels. For plans with flat-benefit or nonpay-related pension benefit formulas, the accumulated benefit obligation and the projected benefit obligation are the same.

+ References

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 132R

-Paragraph 5

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-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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-Name Accounting Standards Codification

-Topic 715

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-Name Accounting Standards Codification

-Glossary Accumulated Benefit Obligation

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The amounts in accumulated other comprehensive income related to gains and losses that are not recognized immediately and are expected to be recognized as components of net periodic benefit cost over the next fiscal year that follows the most recent annual statement of financial position presented.

+ References

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

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-Name Statement of Financial Accounting Standard (FAS)

-Number 132R

-Paragraph 5

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The amounts in accumulated other comprehensive income related to prior service cost or credit expected to be recognized as components of net periodic benefit cost over the next fiscal year that follows the most recent annual statement of financial position presented.

+ References

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 132R

-Paragraph 5

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

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- Definition

The increase in the fair value of plan assets from contributions made by the employer.

+ References

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The employer's best estimate, as soon as it can be reasonably determined, of contributions expected to be paid to the plan during the next fiscal year beginning after the date of the latest statement of financial position. Estimated contributions may be presented in the aggregate combining (1) contributions required by funding regulations or laws, (2) discretionary contributions, and (3) noncash contributions.

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- Definition

Target allocation maximum percentage of investments in debt securities to total plan assets presented on a weighted-average basis as of the measurement date of the latest statement of financial position.

+ References

No definition available.

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Target allocation minimum percentage of investments in debt securities to total plan assets presented on a weighted-average basis as of the measurement date of the latest statement of financial position.

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-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

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-Paragraph 5

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Target allocation maximum percentage of investments in equity securities to total plan assets presented on a weighted-average basis as of the measurement date of the latest statement of financial position.

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Target allocation minimum percentage of investments in equity securities to total plan assets presented on a weighted-average basis as of the measurement date of the latest statement of financial position.

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Target allocation maximum percentage in other than debt securities, equity securities, and real estate to total plan assets presented on a weighted-average basis as of the measurement date of the latest statement of financial position.

+ References

No definition available.

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Target allocation minimum percentage in other than debt securities, equity securities, and real estate to total plan assets presented on a weighted-average basis as of the measurement date of the latest statement of financial position.

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- Definition

The amount of the cost recognized during the period for defined contribution plans.

+ References

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 132R

-Paragraph 11

-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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-Name Accounting Standards Codification

-Topic 715

-SubTopic 70

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