Loss And Loss Adjustment Expense Reserves (RMBS Recoveries) (Narrative) (Details) (USD $)	3 Months Ended	6 Months Ended	12 Months Ended
Dec. 31, 2010	Jun. 30, 2011	Dec. 31, 2010
Estimated insurance recoveries, after income taxes	$ 1,600,000,000	$ 1,800,000,000	$ 1,600,000,000
Income tax rate calculated		35.00%
Percentage of ineligible mortgage loans		80.00%
Percentage of recognized estimated recoveries in relationship to consolidated total shareholder's equity		95.00%	58.00%
Percentage of statutory measures		60.00%	59.00%
Contract Claims On Ineligble Mortgages		4,600,000,000
Settlement received for assured guaranty put-back claims		1,100,000,000
Repurchase request resolved	8,000,000,000
Aggregate of estimated potential recoveries		2,700,000,000
Reviewed [Member] \| RMBS [Member]
Number of mortgage loans reviewed		50,000
RMBS [Member]
Estimated insurance recoveries		2,700,000,000
Insurance loss recoverable		1,800,000,000
Loan repurchase commitments		$ 905,000,000
Number of individual mortgages within securitizations, minimum		500,000
Number of insured issues reviewed		32
Breach rate percentage		80.00%
Sum of probabilities assigned to all scenarios		100.00%
Current risk-free rate associated with underlying transaction, range, minimum		1.32%
Current risk-free rate associated with underlying transaction, range, maximum		3.14%

Aggregate Of Estimated Potential Recoveries

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- Definition

Amount Of Repurchase Request Resolved Related To Ineligible Loans

+ Details

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- Definition

Breach Rate Percentage

+ Details

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- Definition

Amount of Contract Claims on Ineligble Mortgage

+ Details

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- Definition

Current Risk Free Rate Associated With Underlying Transaction, Range, Maximum

+ Details

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- Definition

Current Risk Free Rate Associated With Underlying Transaction, Range, Minimum

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- Definition

Carrying amount as of the balance sheet date of amounts expected to be recovered under the terms of insurance contracts after income taxes.

+ Details

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- Definition

Income tax rate used to calculate estimated insurance recoveries, after income taxes.

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- Definition

Carrying amount as of the balance sheet date of paid insurance policy claims and LAE expense expected to be recovered.

+ Details

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- Definition

The fair value of financial instruments that represent the right of the Trust against the seller/servicer for loans that were not compliant with the representations and warranties of the loan underwriting. The Trust has the right to demand that the transferor replace ineligible loans with a compliant loan or repurchase the non-compliant loan.

+ Details

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- Definition

Number Of Insured Issues Reviewed

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- Definition

Number Of Mortgage Loans Reviewed

+ Details

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- Definition

Percentage Of Ineligible Mortgage Loans

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- Definition

Percentage Of Recognized Estimated Recoveries In Relationship To Consolidated Total Shareholders Equity

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- Definition

Percentage Of Statutory Measures

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- Definition

Settlement Received For Assured Guaranty Put Back Claims

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- Definition

Sum Of Probabilities Assigned To All Scenarios

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- Definition

Carrying amount as of the balance sheet date of amounts expected to be recovered under the terms of insurance contracts.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Section 02
-Paragraph 17
-Article 5

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.17)
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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- Definition

Indicates the number of mortgages under each classification.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 948
-SubTopic 310
-Section S99
-Paragraph 1
-Subparagraph (SX 210.12-29.3)
-URI http://asc.fasb.org/extlink&oid=6589523&loc=d3e617274-123014

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Section 04
-Paragraph c
-Subparagraph Schedule IV
-Article 5

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Article 12
-Section 29
-Paragraph 3

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 205
-SubTopic 10
-Section S99
-Paragraph 6
-Subparagraph (SX 210.5-04.(c) Schedule IV)
-URI http://asc.fasb.org/extlink&oid=6882300&loc=d3e5864-122674

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