Investment Portfolio (Details Textual) (USD $) In Thousands, except Per Share data, unless otherwise specified	6 Months Ended	12 Months Ended
Jun. 30, 2012 Settlement Securities	Dec. 31, 2011
Investment Portfolio (Textual) [Abstract]
Number of Investments in Money market securities	6
Percentage of available-for-sale investments collateralized by US government agency debentures	69.00%	76.00%
Average price of an asset-backed security at par	$ 0.06
Net unrealized gains on securities classified as available-for-sale, net of tax	$ 22,887	$ 21,479
Number of security settlements received	2
Change to fair value of investments rated A or better using lowest rating		less than $0.1 million
Percentage of available-for-sale portfolio priced by third party pricing service	60.00%	69.00%
Percentage of available-for-sale portfolio priced by broker pricing	18.00%	13.00%
Percentage of available-for-sale portfolio priced by internal pricing	22.00%	18.00%

The percentage of the entity's available-for-sale portfolio for which the fair value was determined by broker pricing.

No definition available.

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- Definition

The percentage of the entity's available-for-sale portfolio for which the fair value was determined by internal pricing.

+ References

No definition available.

+ Details

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- Definition

The percentage of the entity's available-for-sale portfolio for which the fair value was determined by a third party pricing service.

+ References

No definition available.

+ Details

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- Definition

Average price average price of asset backed security at par.

+ References

No definition available.

+ Details

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- Definition

The change to the fair value of the available-for-sale securities rated A or better had the entity used the lowest rather than highest rating from the rating agencies.

+ References

No definition available.

+ Details

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- Details

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- Definition

Number of investments in money market securities.

+ References

No definition available.

+ Details

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- Definition

The number of security settlements received by the entity during the reporting period.

+ References

No definition available.

+ Details

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- Definition

The percentage of available-for-sale investments held by the entity that are collateralized by United States government agency debentures.

+ References

No definition available.

+ Details

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- Definition

Accumulated appreciation or loss, net of tax, in value of the total of available-for-sale securities at the end of an accounting period.

+ References

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 130

-Paragraph 26

-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 220

-SubTopic 10

-Section 45

-Paragraph 10A

-Subparagraph (e)

-URI http://asc.fasb.org/extlink&oid=20435746&loc=SL7669646-108580

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 220

-SubTopic 10

-Section 45

-Paragraph 14

-URI http://asc.fasb.org/extlink&oid=20435746&loc=d3e681-108580

Reference 4: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 220

-SubTopic 10

-Section 45

-Paragraph 11

-URI http://asc.fasb.org/extlink&oid=20435746&loc=d3e637-108580

Reference 5: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 220

-SubTopic 10

-Section 45

-Paragraph 14A

-URI http://asc.fasb.org/extlink&oid=20435746&loc=SL7669686-108580

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