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Fair Value Measurement (Company's Assets And Liabilities Measured At Fair Value On Recurring Basis) (Detail) (USD $) In Millions, unless otherwise specified | Jun. 30, 2012 | Dec. 31, 2011
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Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Fair value financial assets measured on recurring basis | $ 12,718 |  | $ 16,206
Fair value financial liabilities measured on recurring basis | 7,329 |  | 10,946
Cash and Cash Equivalents [Member] |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Fair value financial assets measured on recurring basis | 269 |  | 473
Cash |  |  | 160
Variable Interest Entity [Member] | Cash and Cash Equivalents [Member] |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Fair value financial assets measured on recurring basis | 145 |  |
Variable Interest Entity [Member] | Loans Receivable [Member] |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Fair value financial assets measured on recurring basis | 1,903 |  | 2,046
State And Municipal Bonds [Member] | Variable Interest Entity [Member] |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Fair value financial assets measured on recurring basis | 40 |  |
Money Market Securities [Member] |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Fair value financial assets measured on recurring basis | 641 |  | 912
Money Market Securities [Member] | Variable Interest Entity [Member] |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Fair value financial assets measured on recurring basis | 109 |  | 199
Perpetual Preferred Securities [Member] |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Fair value financial assets measured on recurring basis | 49 |  | 107
Medium-term Notes [Member] |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Fair value financial liabilities measured on recurring basis | 151 |  | 165
Total Investments [Member] |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Fair value financial assets measured on recurring basis | 7,093 |  | 8,682
Fixed-Maturity Investments [Member] |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Fair value financial assets measured on recurring basis | 6,373 |  | 7,628
Fixed-Maturity Investments [Member] | Variable Interest Entity [Member] |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Fair value financial assets measured on recurring basis | 2,121 |  | 3,117
Fixed-Maturity Investments [Member] | Other-Fixed Maturity Investments [Member] |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Fair value financial assets measured on recurring basis | 10 |  | 15
Fixed-Maturity Investments [Member] | Corporate Obligations [Member] | Variable Interest Entity [Member] |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Fair value financial assets measured on recurring basis | 311 |  | 239
Fixed-Maturity Investments [Member] | Residential Mortgage-Backed Securities [Member] | Mortgage-Backed Securities [Member] | Variable Interest Entity [Member] |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Fair value financial assets measured on recurring basis |  |  | 3
Fixed-Maturity Investments [Member] | Residential Mortgage-Backed Non-Agency [Member] | Mortgage-Backed Securities [Member] | Variable Interest Entity [Member] |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Fair value financial assets measured on recurring basis | 821 |  | 1,458
Fixed-Maturity Investments [Member] | Commercial Mortgage-Backed [Member] | Mortgage-Backed Securities [Member] | Variable Interest Entity [Member] |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Fair value financial assets measured on recurring basis | 417 |  | 581
Fixed-Maturity Investments [Member] | Collateralized Debt Obligations [Member] | Asset-Backed Securities [Member] | Variable Interest Entity [Member] |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Fair value financial assets measured on recurring basis | 369 |  | 533
Fixed-Maturity Investments [Member] | Other Asset-Backed [Member] | Asset-Backed Securities [Member] | Variable Interest Entity [Member] |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Fair value financial assets measured on recurring basis | 203 |  | 303
Fixed-Maturity Investments [Member] | Taxable Bonds [Member] |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Fair value financial assets measured on recurring basis | 5,293 |  | 6,448
Fixed-Maturity Investments [Member] | Taxable Bonds [Member] | U.S. Treasury And Government Agency [Member] |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Fair value financial assets measured on recurring basis | 1,112 |  | 1,141
Fixed-Maturity Investments [Member] | Taxable Bonds [Member] | Foreign Governments [Member] |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Fair value financial assets measured on recurring basis | 352 |  | 350
Fixed-Maturity Investments [Member] | Taxable Bonds [Member] | Corporate Obligations [Member] |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Fair value financial assets measured on recurring basis | 1,241 |  | 1,739
Fixed-Maturity Investments [Member] | Taxable Bonds [Member] | Residential Mortgage-Backed Securities [Member] | Mortgage-Backed Securities [Member] |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Fair value financial assets measured on recurring basis | 1,116 |  | 1,284
Fixed-Maturity Investments [Member] | Taxable Bonds [Member] | Residential Mortgage-Backed Non-Agency [Member] | Mortgage-Backed Securities [Member] |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Fair value financial assets measured on recurring basis | 184 |  | 367
Fixed-Maturity Investments [Member] | Taxable Bonds [Member] | Commercial Mortgage-Backed [Member] | Mortgage-Backed Securities [Member] |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Fair value financial assets measured on recurring basis | 47 |  | 58
Fixed-Maturity Investments [Member] | Taxable Bonds [Member] | Collateralized Debt Obligations [Member] | Asset-Backed Securities [Member] |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Fair value financial assets measured on recurring basis | 102 |  | 138
Fixed-Maturity Investments [Member] | Taxable Bonds [Member] | Other Asset-Backed [Member] | Asset-Backed Securities [Member] |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Fair value financial assets measured on recurring basis | 200 |  | 447
Fixed-Maturity Investments [Member] | Taxable Bonds [Member] | State And Municipal Bonds [Member] |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Fair value financial assets measured on recurring basis | 939 |  | 924
Fixed-Maturity Investments [Member] | Tax-Exempt Bonds [Member] | State And Municipal Bonds [Member] |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Fair value financial assets measured on recurring basis | 1,070 |  | 1,165
Total Other Investments [Member] |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Fair value financial assets measured on recurring basis | 30 |  | 35
Derivative Assets [Member] |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Fair value financial assets measured on recurring basis | 5 |  | 2
Derivative Assets [Member] | Credit Derivatives [Member] | Insured Derivatives [Member] |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Fair value financial assets measured on recurring basis | 3 |  |
Derivative Assets [Member] | Credit Derivatives [Member] | Non-Insured Derivatives [Member] |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Fair value financial assets measured on recurring basis |  |  | 1
Derivative Assets [Member] | Credit Derivatives [Member] | Variable Interest Entity [Member] |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Fair value financial assets measured on recurring basis |  |  | 447
Derivative Assets [Member] | Interest Rate Derivatives [Member] | Non-Insured Derivatives [Member] |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Fair value financial assets measured on recurring basis | 2 |  | 94
Derivative Assets [Member] | Interest Rate Derivatives [Member] | Variable Interest Entity [Member] |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Fair value financial assets measured on recurring basis | 1 |  | 3
Derivative Assets [Member] | Other Derivatives [Member] | Non-Insured Derivatives [Member] |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Fair value financial assets measured on recurring basis |  |  | (93)
Assets Of Consolidated VIEs [Member] | Loan Repurchase Commitments [Member] |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Fair value financial assets measured on recurring basis | 1,032 |  | 1,077
Derivative Liabilities [Member] | Credit Derivatives [Member] | Insured Derivatives [Member] |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Fair value financial liabilities measured on recurring basis | 3,302 |  | 4,808
Derivative Liabilities [Member] | Credit Derivatives [Member] | Non-Insured Derivatives [Member] |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Fair value financial liabilities measured on recurring basis |  |  | 445
Derivative Liabilities [Member] | Credit Derivatives [Member] | Variable Interest Entity [Member] |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Fair value financial liabilities measured on recurring basis |  |  | 527
Derivative Liabilities [Member] | Interest Rate Derivatives [Member] | Non-Insured Derivatives [Member] |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Fair value financial liabilities measured on recurring basis | 26 |  | 4
Derivative Liabilities [Member] | Interest Rate Derivatives [Member] | Variable Interest Entity [Member] |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Fair value financial liabilities measured on recurring basis | 165 |  | 281
Derivative Liabilities [Member] | Currency Derivatives [Member] | Non-Insured Derivatives [Member] |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Fair value financial liabilities measured on recurring basis | 1 |  | (93)
Derivative Liabilities [Member] | Currency Derivatives [Member] | Variable Interest Entity [Member] |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Fair value financial liabilities measured on recurring basis | 21 |  | 17
Other Liabilities [Member] | Warrant [Member] |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Fair value financial liabilities measured on recurring basis | 25 |  | 38
Variable Interest Entity Notes [Member] | Variable Interest Entity [Member] |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Fair value financial liabilities measured on recurring basis | 3,638 |  | 4,754
Quoted Prices In Active Markets for Identical Assets (Level 1) [Member] |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Fair value financial assets measured on recurring basis | 2,298 |  | 3,085
Quoted Prices In Active Markets for Identical Assets (Level 1) [Member] | Cash and Cash Equivalents [Member] |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Fair value financial assets measured on recurring basis | 269 |  | 473
Cash |  |  | 160
Quoted Prices In Active Markets for Identical Assets (Level 1) [Member] | Variable Interest Entity [Member] | Cash and Cash Equivalents [Member] |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Fair value financial assets measured on recurring basis | 145 |  |
Quoted Prices In Active Markets for Identical Assets (Level 1) [Member] | Money Market Securities [Member] |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Fair value financial assets measured on recurring basis | 641 |  | 912
Quoted Prices In Active Markets for Identical Assets (Level 1) [Member] | Money Market Securities [Member] | Variable Interest Entity [Member] |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Fair value financial assets measured on recurring basis | 109 |  | 199
Quoted Prices In Active Markets for Identical Assets (Level 1) [Member] | Total Investments [Member] |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Fair value financial assets measured on recurring basis | 1,775 |  | 2,253
Quoted Prices In Active Markets for Identical Assets (Level 1) [Member] | Fixed-Maturity Investments [Member] |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Fair value financial assets measured on recurring basis | 1,114 |  | 1,316
Quoted Prices In Active Markets for Identical Assets (Level 1) [Member] | Fixed-Maturity Investments [Member] | Taxable Bonds [Member] |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Fair value financial assets measured on recurring basis | 1,114 |  | 1,316
Quoted Prices In Active Markets for Identical Assets (Level 1) [Member] | Fixed-Maturity Investments [Member] | Taxable Bonds [Member] | U.S. Treasury And Government Agency [Member] |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Fair value financial assets measured on recurring basis | 851 |  | 1,038
Quoted Prices In Active Markets for Identical Assets (Level 1) [Member] | Fixed-Maturity Investments [Member] | Taxable Bonds [Member] | Foreign Governments [Member] |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Fair value financial assets measured on recurring basis | 263 |  | 277
Quoted Prices In Active Markets for Identical Assets (Level 1) [Member] | Fixed-Maturity Investments [Member] | Taxable Bonds [Member] | Corporate Obligations [Member] |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Fair value financial assets measured on recurring basis |  |  | 1
Quoted Prices In Active Markets for Identical Assets (Level 1) [Member] | Total Other Investments [Member] |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Fair value financial assets measured on recurring basis | 20 |  | 25
Significant Other Observable Inputs (Level 2) [Member] |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Fair value financial assets measured on recurring basis | 6,967 |  | 8,576
Fair value financial liabilities measured on recurring basis | 2,100 |  | 2,651
Significant Other Observable Inputs (Level 2) [Member] | State And Municipal Bonds [Member] | Variable Interest Entity [Member] |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Fair value financial assets measured on recurring basis | 40 |  |
Significant Other Observable Inputs (Level 2) [Member] | Perpetual Preferred Securities [Member] |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Fair value financial assets measured on recurring basis | 46 |  | 106
Significant Other Observable Inputs (Level 2) [Member] | Total Investments [Member] |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Fair value financial assets measured on recurring basis | 5,008 |  | 5,746
Significant Other Observable Inputs (Level 2) [Member] | Fixed-Maturity Investments [Member] |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Fair value financial assets measured on recurring basis | 4,962 |  | 5,640
Significant Other Observable Inputs (Level 2) [Member] | Fixed-Maturity Investments [Member] | Variable Interest Entity [Member] |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Fair value financial assets measured on recurring basis | 1,822 |  | 2,735
Significant Other Observable Inputs (Level 2) [Member] | Fixed-Maturity Investments [Member] | Other-Fixed Maturity Investments [Member] |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Fair value financial assets measured on recurring basis | 10 |  | 15
Significant Other Observable Inputs (Level 2) [Member] | Fixed-Maturity Investments [Member] | Corporate Obligations [Member] | Variable Interest Entity [Member] |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Fair value financial assets measured on recurring basis | 216 |  | 170
Significant Other Observable Inputs (Level 2) [Member] | Fixed-Maturity Investments [Member] | Residential Mortgage-Backed Securities [Member] | Mortgage-Backed Securities [Member] | Variable Interest Entity [Member] |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Fair value financial assets measured on recurring basis |  |  | 3
Significant Other Observable Inputs (Level 2) [Member] | Fixed-Maturity Investments [Member] | Residential Mortgage-Backed Non-Agency [Member] | Mortgage-Backed Securities [Member] | Variable Interest Entity [Member] |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Fair value financial assets measured on recurring basis | 811 |  | 1,437
Significant Other Observable Inputs (Level 2) [Member] | Fixed-Maturity Investments [Member] | Commercial Mortgage-Backed [Member] | Mortgage-Backed Securities [Member] | Variable Interest Entity [Member] |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Fair value financial assets measured on recurring basis | 405 |  | 559
Significant Other Observable Inputs (Level 2) [Member] | Fixed-Maturity Investments [Member] | Collateralized Debt Obligations [Member] | Asset-Backed Securities [Member] | Variable Interest Entity [Member] |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Fair value financial assets measured on recurring basis | 229 |  | 330
Significant Other Observable Inputs (Level 2) [Member] | Fixed-Maturity Investments [Member] | Other Asset-Backed [Member] | Asset-Backed Securities [Member] | Variable Interest Entity [Member] |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Fair value financial assets measured on recurring basis | 161 |  | 236
Significant Other Observable Inputs (Level 2) [Member] | Fixed-Maturity Investments [Member] | Taxable Bonds [Member] |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Fair value financial assets measured on recurring basis | 3,907 |  | 4,488
Significant Other Observable Inputs (Level 2) [Member] | Fixed-Maturity Investments [Member] | Taxable Bonds [Member] | U.S. Treasury And Government Agency [Member] |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Fair value financial assets measured on recurring basis | 261 |  | 103
Significant Other Observable Inputs (Level 2) [Member] | Fixed-Maturity Investments [Member] | Taxable Bonds [Member] | Foreign Governments [Member] |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Fair value financial assets measured on recurring basis | 77 |  | 62
Significant Other Observable Inputs (Level 2) [Member] | Fixed-Maturity Investments [Member] | Taxable Bonds [Member] | Corporate Obligations [Member] |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Fair value financial assets measured on recurring basis | 1,143 |  | 1,531
Significant Other Observable Inputs (Level 2) [Member] | Fixed-Maturity Investments [Member] | Taxable Bonds [Member] | Residential Mortgage-Backed Securities [Member] | Mortgage-Backed Securities [Member] |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Fair value financial assets measured on recurring basis | 1,112 |  | 1,276
Significant Other Observable Inputs (Level 2) [Member] | Fixed-Maturity Investments [Member] | Taxable Bonds [Member] | Residential Mortgage-Backed Non-Agency [Member] | Mortgage-Backed Securities [Member] |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Fair value financial assets measured on recurring basis | 154 |  | 350
Significant Other Observable Inputs (Level 2) [Member] | Fixed-Maturity Investments [Member] | Taxable Bonds [Member] | Commercial Mortgage-Backed [Member] | Mortgage-Backed Securities [Member] |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Fair value financial assets measured on recurring basis | 20 |  | 34
Significant Other Observable Inputs (Level 2) [Member] | Fixed-Maturity Investments [Member] | Taxable Bonds [Member] | Collateralized Debt Obligations [Member] | Asset-Backed Securities [Member] |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Fair value financial assets measured on recurring basis | 73 |  | 78
Significant Other Observable Inputs (Level 2) [Member] | Fixed-Maturity Investments [Member] | Taxable Bonds [Member] | Other Asset-Backed [Member] | Asset-Backed Securities [Member] |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Fair value financial assets measured on recurring basis | 128 |  | 130
Significant Other Observable Inputs (Level 2) [Member] | Fixed-Maturity Investments [Member] | Taxable Bonds [Member] | State And Municipal Bonds [Member] |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Fair value financial assets measured on recurring basis | 939 |  | 924
Significant Other Observable Inputs (Level 2) [Member] | Fixed-Maturity Investments [Member] | Tax-Exempt Bonds [Member] | State And Municipal Bonds [Member] |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Fair value financial assets measured on recurring basis | 1,045 |  | 1,137
Significant Other Observable Inputs (Level 2) [Member] | Derivative Assets [Member] |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Fair value financial assets measured on recurring basis | 96 |  | 92
Significant Other Observable Inputs (Level 2) [Member] | Derivative Assets [Member] | Credit Derivatives [Member] | Non-Insured Derivatives [Member] |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Fair value financial assets measured on recurring basis |  |  | 1
Significant Other Observable Inputs (Level 2) [Member] | Derivative Assets [Member] | Interest Rate Derivatives [Member] | Non-Insured Derivatives [Member] |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Fair value financial assets measured on recurring basis | 96 |  | 91
Significant Other Observable Inputs (Level 2) [Member] | Derivative Assets [Member] | Interest Rate Derivatives [Member] | Variable Interest Entity [Member] |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Fair value financial assets measured on recurring basis | 1 |  | 3
Significant Other Observable Inputs (Level 2) [Member] | Derivative Liabilities [Member] | Credit Derivatives [Member] | Insured Derivatives [Member] |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Fair value financial liabilities measured on recurring basis | 14 |  | 18
Significant Other Observable Inputs (Level 2) [Member] | Derivative Liabilities [Member] | Credit Derivatives [Member] | Non-Insured Derivatives [Member] |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Fair value financial liabilities measured on recurring basis |  |  | 445
Significant Other Observable Inputs (Level 2) [Member] | Derivative Liabilities [Member] | Interest Rate Derivatives [Member] | Non-Insured Derivatives [Member] |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Fair value financial liabilities measured on recurring basis | 124 |  | 4
Significant Other Observable Inputs (Level 2) [Member] | Derivative Liabilities [Member] | Interest Rate Derivatives [Member] | Variable Interest Entity [Member] |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Fair value financial liabilities measured on recurring basis | 165 |  | 281
Significant Other Observable Inputs (Level 2) [Member] | Derivative Liabilities [Member] | Currency Derivatives [Member] | Non-Insured Derivatives [Member] |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Fair value financial liabilities measured on recurring basis | 1 |  |
Significant Other Observable Inputs (Level 2) [Member] | Other Liabilities [Member] | Warrant [Member] |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Fair value financial liabilities measured on recurring basis | 25 |  | 38
Significant Other Observable Inputs (Level 2) [Member] | Variable Interest Entity Notes [Member] | Variable Interest Entity [Member] |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Fair value financial liabilities measured on recurring basis | 1,771 |  | 1,865
Significant Unobservable Inputs (Level 3) [Member] |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Fair value financial assets measured on recurring basis | 3,551 |  | 4,638
Fair value financial liabilities measured on recurring basis | 5,327 |  | 8,388
Significant Unobservable Inputs (Level 3) [Member] | Variable Interest Entity [Member] | Loans Receivable [Member] |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Fair value financial assets measured on recurring basis | 1,903 |  | 2,046
Significant Unobservable Inputs (Level 3) [Member] | Perpetual Preferred Securities [Member] |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Fair value financial assets measured on recurring basis | 3 | [1] | 1
Significant Unobservable Inputs (Level 3) [Member] | Medium-term Notes [Member] |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Fair value financial liabilities measured on recurring basis | 151 | [1] | 165
Significant Unobservable Inputs (Level 3) [Member] | Total Investments [Member] |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Fair value financial assets measured on recurring basis | 310 |  | 683
Significant Unobservable Inputs (Level 3) [Member] | Fixed-Maturity Investments [Member] |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Fair value financial assets measured on recurring basis | 297 |  | 672
Significant Unobservable Inputs (Level 3) [Member] | Fixed-Maturity Investments [Member] | Variable Interest Entity [Member] |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Fair value financial assets measured on recurring basis | 299 |  | 382
Significant Unobservable Inputs (Level 3) [Member] | Fixed-Maturity Investments [Member] | Corporate Obligations [Member] | Variable Interest Entity [Member] |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Fair value financial assets measured on recurring basis | 95 | [1] | 69
Significant Unobservable Inputs (Level 3) [Member] | Fixed-Maturity Investments [Member] | Residential Mortgage-Backed Non-Agency [Member] | Mortgage-Backed Securities [Member] | Variable Interest Entity [Member] |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Fair value financial assets measured on recurring basis | 10 | [1] | 21
Significant Unobservable Inputs (Level 3) [Member] | Fixed-Maturity Investments [Member] | Commercial Mortgage-Backed [Member] | Mortgage-Backed Securities [Member] | Variable Interest Entity [Member] |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Fair value financial assets measured on recurring basis | 12 | [1] | 22
Significant Unobservable Inputs (Level 3) [Member] | Fixed-Maturity Investments [Member] | Collateralized Debt Obligations [Member] | Asset-Backed Securities [Member] | Variable Interest Entity [Member] |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Fair value financial assets measured on recurring basis | 140 | [1] | 203
Significant Unobservable Inputs (Level 3) [Member] | Fixed-Maturity Investments [Member] | Other Asset-Backed [Member] | Asset-Backed Securities [Member] | Variable Interest Entity [Member] |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Fair value financial assets measured on recurring basis | 42 | [1] | 67
Significant Unobservable Inputs (Level 3) [Member] | Fixed-Maturity Investments [Member] | Taxable Bonds [Member] |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Fair value financial assets measured on recurring basis | 272 |  | 644
Significant Unobservable Inputs (Level 3) [Member] | Fixed-Maturity Investments [Member] | Taxable Bonds [Member] | Foreign Governments [Member] |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Fair value financial assets measured on recurring basis | 12 | [1] | 11
Significant Unobservable Inputs (Level 3) [Member] | Fixed-Maturity Investments [Member] | Taxable Bonds [Member] | Corporate Obligations [Member] |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Fair value financial assets measured on recurring basis | 98 | [1] | 207
Significant Unobservable Inputs (Level 3) [Member] | Fixed-Maturity Investments [Member] | Taxable Bonds [Member] | Residential Mortgage-Backed Securities [Member] | Mortgage-Backed Securities [Member] |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Fair value financial assets measured on recurring basis | 4 | [1] | 8
Significant Unobservable Inputs (Level 3) [Member] | Fixed-Maturity Investments [Member] | Taxable Bonds [Member] | Residential Mortgage-Backed Non-Agency [Member] | Mortgage-Backed Securities [Member] |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Fair value financial assets measured on recurring basis | 30 | [1] | 17
Significant Unobservable Inputs (Level 3) [Member] | Fixed-Maturity Investments [Member] | Taxable Bonds [Member] | Commercial Mortgage-Backed [Member] | Mortgage-Backed Securities [Member] |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Fair value financial assets measured on recurring basis | 27 | [1] | 24
Significant Unobservable Inputs (Level 3) [Member] | Fixed-Maturity Investments [Member] | Taxable Bonds [Member] | Collateralized Debt Obligations [Member] | Asset-Backed Securities [Member] |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Fair value financial assets measured on recurring basis | 29 | [1] | 60
Significant Unobservable Inputs (Level 3) [Member] | Fixed-Maturity Investments [Member] | Taxable Bonds [Member] | Other Asset-Backed [Member] | Asset-Backed Securities [Member] |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Fair value financial assets measured on recurring basis | 72 | [1] | 317
Significant Unobservable Inputs (Level 3) [Member] | Fixed-Maturity Investments [Member] | Tax-Exempt Bonds [Member] | State And Municipal Bonds [Member] |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Fair value financial assets measured on recurring basis | 25 | [1] | 28
Significant Unobservable Inputs (Level 3) [Member] | Total Other Investments [Member] |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Fair value financial assets measured on recurring basis | 10 | [1] | 10
Significant Unobservable Inputs (Level 3) [Member] | Derivative Assets [Member] |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Fair value financial assets measured on recurring basis | 7 |  | 3
Significant Unobservable Inputs (Level 3) [Member] | Derivative Assets [Member] | Credit Derivatives [Member] | Insured Derivatives [Member] |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Fair value financial assets measured on recurring basis | 3 |  |
Significant Unobservable Inputs (Level 3) [Member] | Derivative Assets [Member] | Credit Derivatives [Member] | Variable Interest Entity [Member] |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Fair value financial assets measured on recurring basis |  |  | 447
Significant Unobservable Inputs (Level 3) [Member] | Derivative Assets [Member] | Interest Rate Derivatives [Member] | Non-Insured Derivatives [Member] |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Fair value financial assets measured on recurring basis | 4 | [1] | 3
Significant Unobservable Inputs (Level 3) [Member] | Assets Of Consolidated VIEs [Member] | Loan Repurchase Commitments [Member] |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Fair value financial assets measured on recurring basis | 1,032 |  | 1,077
Significant Unobservable Inputs (Level 3) [Member] | Derivative Liabilities [Member] | Credit Derivatives [Member] | Insured Derivatives [Member] |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Fair value financial liabilities measured on recurring basis | 3,288 |  | 4,790
Significant Unobservable Inputs (Level 3) [Member] | Derivative Liabilities [Member] | Credit Derivatives [Member] | Variable Interest Entity [Member] |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Fair value financial liabilities measured on recurring basis |  |  | 527
Significant Unobservable Inputs (Level 3) [Member] | Derivative Liabilities [Member] | Currency Derivatives [Member] | Variable Interest Entity [Member] |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Fair value financial liabilities measured on recurring basis | 21 | [1] | 17
Significant Unobservable Inputs (Level 3) [Member] | Variable Interest Entity Notes [Member] | Variable Interest Entity [Member] |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Fair value financial liabilities measured on recurring basis | 1,867 |  | 2,889
Counterparty And Cash Collateral Netting [Member] |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Fair value financial assets measured on recurring basis | (98) |  | (93)
Fair value financial liabilities measured on recurring basis | (98) |  | (93)
Counterparty And Cash Collateral Netting [Member] | Derivative Assets [Member] |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Fair value financial assets measured on recurring basis | (98) |  | (93)
Counterparty And Cash Collateral Netting [Member] | Derivative Assets [Member] | Interest Rate Derivatives [Member] | Non-Insured Derivatives [Member] |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Fair value financial assets measured on recurring basis | (98) |  |
Counterparty And Cash Collateral Netting [Member] | Derivative Assets [Member] | Other Derivatives [Member] | Non-Insured Derivatives [Member] |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Fair value financial assets measured on recurring basis |  |  | (93)
Counterparty And Cash Collateral Netting [Member] | Derivative Liabilities [Member] | Interest Rate Derivatives [Member] | Non-Insured Derivatives [Member] |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Fair value financial liabilities measured on recurring basis | (98) |  |
Counterparty And Cash Collateral Netting [Member] | Derivative Liabilities [Member] | Currency Derivatives [Member] | Non-Insured Derivatives [Member] |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Fair value financial liabilities measured on recurring basis |  |  | $ (93)
[1] | Unobservable inputs are either not developed by the Company or do not significantly impact the overall fair values of the aggregate financial assets and liabilities.

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- Definition This element represents the portion of the balance sheet assertion valued at fair value by the entity whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission. This item represents investment securities as of the balance sheet date which may include marketable securities, derivative financial instruments, and investments accounted for under the equity method. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Trading Securities -URI http://asc.fasb.org/extlink&oid=6526789 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 25 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=7534914&loc=d3e22054-111558 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 115 -Paragraph 13 -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 4: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 03 -Paragraph 1 -Subparagraph a, f, g -Article 7 Reference 5: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Available-for-Sale Securities -URI http://asc.fasb.org/extlink&oid=6505594 Reference 6: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 115 -Paragraph 12 -Subparagraph a -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 7: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 35 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=16383099&loc=d3e24584-111560 + Details
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