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Businesses, Developments, Risks And Uncertainties (Details) (USD $) | 9 Months Ended |  |  | 9 Months Ended |  | 3 Months Ended |  |  |
--- | --- | --- | --- | --- | --- | --- | --- | --- | ---
Sep. 30, 2011 | Dec. 31, 2011 | Dec. 31, 2010 | Sep. 30, 2011 CMBS Pools, Investment Grade Corporate CDOs, A Government Supported Entity And A Municipal Gas Facility [Member] | Sep. 30, 2011 ABS CDO [Member] | Sep. 30, 2011 ABS CDO [Member] Decrease Since 2007 [Member] | Sep. 30, 2011 CRE CDO [Member] | Dec. 31, 2011 Primarily Commercial Real Estate [Member] | Sep. 30, 2011 Current Balance [Member] | May 31, 2012 Borrowing Limit [Member] | Sep. 30, 2011 CRE Loan Pools [Member] | Sep. 30, 2011 CMBS Pool [Member]
Business Acquisition [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Statutory capital | $ 2,600,000,000 |  | $ 2,700,000,000 |  |  |  |  |  |  |  |  |
Liquid assets | 824,000,000 |  | 1,200,000,000 |  |  |  |  |  |  |  |  |
Commuted gross insured exposure |  |  |  | 12,200,000,000 |  |  |  | 10,600,000,000 |  |  |  |
Insured par exposure |  |  |  |  |  |  | 6,900,000,000 |  |  |  | 3,600,000,000 | 33,400,000,000
ABS CDO gross par outstanding |  |  |  |  |  | 29,000,000,000 |  |  |  |  |  |
Gross par outstanding |  |  |  |  | 6,900,000,000 |  |  |  |  |  |  |
Book value deficit | 610,000,000 |  |  |  |  |  |  |  |  |  |  |
Intercompany tax payments | 194,000,000 |  |  |  |  |  |  |  |  |  |  |
Percent loss and unearned premium reserves in qualifying assets | 50.00% |  |  |  |  |  |  |  |  |  |  |
Contingency reserve release to surplus | 318,000,000 |  |  |  |  |  |  |  |  |  |  |
Secured loan balance |  |  |  |  |  |  |  |  | 600,000,000 | 450,000,000 |  |
Capital contribution |  | $ 50,000,000 |  |  |  |  |  |  |  |  |  |

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