Net Premiums Earned (Details Textual) (USD $) In Thousands, unless otherwise specified	3 Months Ended	6 Months Ended	12 Months Ended
Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011	Dec. 31, 2011
Net Premiums Earned (Textual) [Abstract]
Weighted average risk-free rate			2.50%		2.60%
Weighted average period of future premiums			10 years 3 months 18 days		10 years
Transactions with non-investment grade internal ratings			43.00%		43.00%
Non-investment grade MBS			11.00%		11.00%
Student loan transactions			12.00%		11.00%
Premium receivables uncollectible and written off relating to a non-investment grade obligation	$ 12,758		$ 17,175
Premium receivables uncollectible relating to a non-investment grade obligation	108,105		108,105		90,930
Past due premiums on policies insuring non-investment grade obligations	500		500
Accelerated premium revenue for retired obligations	$ 35,866	$ 11,331	$ 51,656	$ 11,261

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Percentage of premiums receivable related to non investment grade RMBS transactions.

+ References

No definition available.

+ Details

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- Definition

Percentage of premiums receivable related to student loan transactions.

+ References

No definition available.

+ Details

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- Definition

Percentage premiums receivable related to transactions with non-investment grade internal ratings.

+ References

No definition available.

+ Details

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- Definition

Past due premiums receivable not written off related to non-investment grade obligation.

+ References

No definition available.

+ Details

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- Definition

Premiums deemed uncollectible and written off related to non-investment grade obligation.

+ References

No definition available.

+ Details

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- Definition

Premiums deemed uncollectible related to non-investment grade obligation.

+ References

No definition available.

+ Details

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- Definition

This element represents the amount of premium revenue on financial guarantee insurance contracts recognized during the period that was accelerated for revenue recognition purposes.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 944

-SubTopic 605

-Section 50

-Paragraph 4

-Subparagraph (a)

-URI http://asc.fasb.org/extlink&oid=6933581&loc=SL5749298-161291

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 163

-Paragraph 30

-Subparagraph d

-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.

+ Details

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- Definition

Weighted average period over which premium receivable for financial guarantee insurance contracts is collected where premium is received over the contract period, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

+ Details

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- Definition

This element represents the weighted average risk free rate used to discount the premiums expected to be collected for financial guarantee insurance contracts where the premium is to be received over the contract period.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 944

-SubTopic 310

-Section 50

-Paragraph 3

-Subparagraph (a)(4)

-URI http://asc.fasb.org/extlink&oid=6933075&loc=SL5748726-161290

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 163

-Paragraph 30

-Subparagraph a(3)

-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.

+ Details

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