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Fair Value Of Financial Instruments (Company's Assets And Liabilities Measured At Fair Value On A Recurring Basis) (Details) (USD $) In Millions | Sep. 30, 2011 | Dec. 31, 2010
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Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Fair value financial assets measured on recurring basis | $ 18,000 | $ 21,227
Fair value financial liabilities measured on recurring basis | 12,417 | 13,575
Variable Interest Entity, Primary Beneficiary [Member] | Loans Receivable [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Fair value financial assets measured on recurring basis | 2,218 | 2,183
Variable Interest Entity, Primary Beneficiary [Member] | Loans Receivable [Member] | Fair Value, Inputs, Level 3 [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Fair value financial assets measured on recurring basis | 2,218 | 2,183
Variable Interest Entity, Primary Beneficiary [Member] | Loan Repurchase Commitments [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Fair value financial assets measured on recurring basis |  | 835
Variable Interest Entity, Primary Beneficiary [Member] | Loan Repurchase Commitments [Member] | Fair Value, Inputs, Level 3 [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Fair value financial assets measured on recurring basis |  | 835
Loan Repurchase Commitments [Member] | Assets Of Consolidated VIEs [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Fair value financial assets measured on recurring basis | 938 |
Loan Repurchase Commitments [Member] | Assets Of Consolidated VIEs [Member] | Fair Value, Inputs, Level 3 [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Fair value financial assets measured on recurring basis | 938 |
Variable Interest Entity, Primary Beneficiary [Member] | Collateralized Debt Obligations [Member] | Fixed-Maturity Investments [Member] | Asset-Backed Securities [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Fair value financial assets measured on recurring basis | 643 | 828
Variable Interest Entity, Primary Beneficiary [Member] | Collateralized Debt Obligations [Member] | Fixed-Maturity Investments [Member] | Asset-Backed Securities [Member] | Fair Value, Inputs, Level 2 [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Fair value financial assets measured on recurring basis | 437 | 583
Variable Interest Entity, Primary Beneficiary [Member] | Collateralized Debt Obligations [Member] | Fixed-Maturity Investments [Member] | Asset-Backed Securities [Member] | Fair Value, Inputs, Level 3 [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Fair value financial assets measured on recurring basis | 206 | 245
Variable Interest Entity, Primary Beneficiary [Member] | Residential Mortgage-Backed Securities [Member] | Fixed-Maturity Investments [Member] | Mortgage-Backed Securities [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Fair value financial assets measured on recurring basis | 4 | 37
Variable Interest Entity, Primary Beneficiary [Member] | Residential Mortgage-Backed Securities [Member] | Fixed-Maturity Investments [Member] | Mortgage-Backed Securities [Member] | Fair Value, Inputs, Level 2 [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Fair value financial assets measured on recurring basis | 4 | 37
Variable Interest Entity, Primary Beneficiary [Member] | Commercial Mortgage-Backed [Member] | Fixed-Maturity Investments [Member] | Mortgage-Backed Securities [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Fair value financial assets measured on recurring basis | 612 | 930
Variable Interest Entity, Primary Beneficiary [Member] | Commercial Mortgage-Backed [Member] | Fixed-Maturity Investments [Member] | Mortgage-Backed Securities [Member] | Fair Value, Inputs, Level 2 [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Fair value financial assets measured on recurring basis | 595 | 907
Variable Interest Entity, Primary Beneficiary [Member] | Commercial Mortgage-Backed [Member] | Fixed-Maturity Investments [Member] | Mortgage-Backed Securities [Member] | Fair Value, Inputs, Level 3 [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Fair value financial assets measured on recurring basis | 17 | 23
Variable Interest Entity, Primary Beneficiary [Member] | Fixed-Maturity Investments [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Fair value financial assets measured on recurring basis | 3,590 | 5,431
Variable Interest Entity, Primary Beneficiary [Member] | Fixed-Maturity Investments [Member] | Mortgage-Backed Securities [Member] | Residential Mortgage-Backed Non-Agency [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Fair value financial assets measured on recurring basis | 1,718 | 2,746
Variable Interest Entity, Primary Beneficiary [Member] | Fixed-Maturity Investments [Member] | Mortgage-Backed Securities [Member] | Residential Mortgage-Backed Non-Agency [Member] | Fair Value, Inputs, Level 2 [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Fair value financial assets measured on recurring basis | 1,703 | 2,706
Variable Interest Entity, Primary Beneficiary [Member] | Fixed-Maturity Investments [Member] | Mortgage-Backed Securities [Member] | Residential Mortgage-Backed Non-Agency [Member] | Fair Value, Inputs, Level 3 [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Fair value financial assets measured on recurring basis | 15 | 40
Variable Interest Entity, Primary Beneficiary [Member] | Fixed-Maturity Investments [Member] | Asset-Backed Securities [Member] | Other Asset-Backed [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Fair value financial assets measured on recurring basis | 346 | 435
Variable Interest Entity, Primary Beneficiary [Member] | Fixed-Maturity Investments [Member] | Asset-Backed Securities [Member] | Other Asset-Backed [Member] | Fair Value, Inputs, Level 2 [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Fair value financial assets measured on recurring basis | 275 | 352
Variable Interest Entity, Primary Beneficiary [Member] | Fixed-Maturity Investments [Member] | Asset-Backed Securities [Member] | Other Asset-Backed [Member] | Fair Value, Inputs, Level 3 [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Fair value financial assets measured on recurring basis | 71 | 83
Variable Interest Entity, Primary Beneficiary [Member] | Fixed-Maturity Investments [Member] | Asset-Backed Securities [Member] | State And Municipal Bonds [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Fair value financial assets measured on recurring basis |  | 4
Variable Interest Entity, Primary Beneficiary [Member] | Fixed-Maturity Investments [Member] | Asset-Backed Securities [Member] | State And Municipal Bonds [Member] | Fair Value, Inputs, Level 2 [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Fair value financial assets measured on recurring basis |  | 4
Variable Interest Entity, Primary Beneficiary [Member] | Fixed-Maturity Investments [Member] | U.S. Treasury And Government Agency [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Fair value financial assets measured on recurring basis |  | 4
Variable Interest Entity, Primary Beneficiary [Member] | Fixed-Maturity Investments [Member] | U.S. Treasury And Government Agency [Member] | Fair Value, Inputs, Level 1 [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Fair value financial assets measured on recurring basis |  | 4
Variable Interest Entity, Primary Beneficiary [Member] | Fixed-Maturity Investments [Member] | Corporate Obligations [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Fair value financial assets measured on recurring basis | 267 | 447
Variable Interest Entity, Primary Beneficiary [Member] | Fixed-Maturity Investments [Member] | Corporate Obligations [Member] | Fair Value, Inputs, Level 1 [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Fair value financial assets measured on recurring basis |  | 7
Variable Interest Entity, Primary Beneficiary [Member] | Fixed-Maturity Investments [Member] | Corporate Obligations [Member] | Fair Value, Inputs, Level 2 [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Fair value financial assets measured on recurring basis | 204 | 360
Variable Interest Entity, Primary Beneficiary [Member] | Fixed-Maturity Investments [Member] | Corporate Obligations [Member] | Fair Value, Inputs, Level 3 [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Fair value financial assets measured on recurring basis | 63 | 80
Variable Interest Entity, Primary Beneficiary [Member] | Fixed-Maturity Investments [Member] | Fair Value, Inputs, Level 1 [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Fair value financial assets measured on recurring basis |  | 11
Variable Interest Entity, Primary Beneficiary [Member] | Fixed-Maturity Investments [Member] | Fair Value, Inputs, Level 2 [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Fair value financial assets measured on recurring basis | 3,218 | 4,949
Variable Interest Entity, Primary Beneficiary [Member] | Fixed-Maturity Investments [Member] | Fair Value, Inputs, Level 3 [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Fair value financial assets measured on recurring basis | 372 | 471
Variable Interest Entity, Primary Beneficiary [Member] | Derivative Assets [Member] | Credit Derivatives [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Fair value financial assets measured on recurring basis | 708 | 687
Variable Interest Entity, Primary Beneficiary [Member] | Derivative Assets [Member] | Credit Derivatives [Member] | Fair Value, Inputs, Level 3 [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Fair value financial assets measured on recurring basis | 708 | 687
Variable Interest Entity, Primary Beneficiary [Member] | Derivative Assets [Member] | Interest Rate Derivatives [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Fair value financial assets measured on recurring basis | 5 | 12
Variable Interest Entity, Primary Beneficiary [Member] | Derivative Assets [Member] | Interest Rate Derivatives [Member] | Fair Value, Inputs, Level 2 [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Fair value financial assets measured on recurring basis | 5 | 12
Variable Interest Entity, Primary Beneficiary [Member] | Derivative Liabilities [Member] | Credit Derivatives [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Fair value financial liabilities measured on recurring basis | 1,473 | 1,455
Variable Interest Entity, Primary Beneficiary [Member] | Derivative Liabilities [Member] | Credit Derivatives [Member] | Fair Value, Inputs, Level 3 [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Fair value financial liabilities measured on recurring basis | 1,473 | 1,455
Variable Interest Entity, Primary Beneficiary [Member] | Derivative Liabilities [Member] | Interest Rate Derivatives [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Fair value financial liabilities measured on recurring basis | 397 | 635
Variable Interest Entity, Primary Beneficiary [Member] | Derivative Liabilities [Member] | Interest Rate Derivatives [Member] | Fair Value, Inputs, Level 2 [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Fair value financial liabilities measured on recurring basis | 397 | 635
Variable Interest Entity, Primary Beneficiary [Member] | Derivative Liabilities [Member] | Currency Derivatives [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Fair value financial liabilities measured on recurring basis | 18 | 14
Variable Interest Entity, Primary Beneficiary [Member] | Derivative Liabilities [Member] | Currency Derivatives [Member] | Fair Value, Inputs, Level 3 [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Fair value financial liabilities measured on recurring basis | 18 | 14
Variable Interest Entity, Primary Beneficiary [Member] | Money Market Securities [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Fair value financial assets measured on recurring basis | 218 | 150
Variable Interest Entity, Primary Beneficiary [Member] | Money Market Securities [Member] | Fair Value, Inputs, Level 1 [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Fair value financial assets measured on recurring basis | 218 | 150
Variable Interest Entity, Primary Beneficiary [Member] | Variable Interest Entity Notes [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Fair value financial liabilities measured on recurring basis | 5,123 | 6,680
Variable Interest Entity, Primary Beneficiary [Member] | Variable Interest Entity Notes [Member] | Fair Value, Inputs, Level 2 [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Fair value financial liabilities measured on recurring basis | 1,992 | 2,007
Variable Interest Entity, Primary Beneficiary [Member] | Variable Interest Entity Notes [Member] | Fair Value, Inputs, Level 3 [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Fair value financial liabilities measured on recurring basis | 3,131 | 4,673
Collateralized Debt Obligations [Member] | Fixed-Maturity Investments [Member] | Taxable Bonds [Member] | Asset-Backed Securities [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Fair value financial assets measured on recurring basis | 151 | 299
Collateralized Debt Obligations [Member] | Fixed-Maturity Investments [Member] | Taxable Bonds [Member] | Asset-Backed Securities [Member] | Fair Value, Inputs, Level 2 [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Fair value financial assets measured on recurring basis | 84 | 108
Collateralized Debt Obligations [Member] | Fixed-Maturity Investments [Member] | Taxable Bonds [Member] | Asset-Backed Securities [Member] | Fair Value, Inputs, Level 3 [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Fair value financial assets measured on recurring basis | 67 | 191
Residential Mortgage-Backed Securities [Member] | Fixed-Maturity Investments [Member] | Taxable Bonds [Member] | Mortgage-Backed Securities [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Fair value financial assets measured on recurring basis | 1,420 | 1,589
Residential Mortgage-Backed Securities [Member] | Fixed-Maturity Investments [Member] | Taxable Bonds [Member] | Mortgage-Backed Securities [Member] | Fair Value, Inputs, Level 2 [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Fair value financial assets measured on recurring basis | 1,419 | 1,548
Residential Mortgage-Backed Securities [Member] | Fixed-Maturity Investments [Member] | Taxable Bonds [Member] | Mortgage-Backed Securities [Member] | Fair Value, Inputs, Level 3 [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Fair value financial assets measured on recurring basis | 1 | 41
Commercial Mortgage-Backed [Member] | Fixed-Maturity Investments [Member] | Taxable Bonds [Member] | Mortgage-Backed Securities [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Fair value financial assets measured on recurring basis | 67 | 161
Commercial Mortgage-Backed [Member] | Fixed-Maturity Investments [Member] | Taxable Bonds [Member] | Mortgage-Backed Securities [Member] | Fair Value, Inputs, Level 2 [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Fair value financial assets measured on recurring basis | 35 | 120
Commercial Mortgage-Backed [Member] | Fixed-Maturity Investments [Member] | Taxable Bonds [Member] | Mortgage-Backed Securities [Member] | Fair Value, Inputs, Level 3 [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Fair value financial assets measured on recurring basis | 32 | 41
Fixed-Maturity Investments [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Fair value financial assets measured on recurring basis | 9,454 | 11,159
Fixed-Maturity Investments [Member] | Taxable Bonds [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Fair value financial assets measured on recurring basis | 6,594 | 8,304
Fixed-Maturity Investments [Member] | Taxable Bonds [Member] | Mortgage-Backed Securities [Member] | Residential Mortgage-Backed Non-Agency [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Fair value financial assets measured on recurring basis | 446 | 462
Fixed-Maturity Investments [Member] | Taxable Bonds [Member] | Mortgage-Backed Securities [Member] | Residential Mortgage-Backed Non-Agency [Member] | Fair Value, Inputs, Level 2 [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Fair value financial assets measured on recurring basis | 421 | 414
Fixed-Maturity Investments [Member] | Taxable Bonds [Member] | Mortgage-Backed Securities [Member] | Residential Mortgage-Backed Non-Agency [Member] | Fair Value, Inputs, Level 3 [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Fair value financial assets measured on recurring basis | 25 | 48
Fixed-Maturity Investments [Member] | Taxable Bonds [Member] | Asset-Backed Securities [Member] | Other Asset-Backed [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Fair value financial assets measured on recurring basis | 457 | 660
Fixed-Maturity Investments [Member] | Taxable Bonds [Member] | Asset-Backed Securities [Member] | Other Asset-Backed [Member] | Fair Value, Inputs, Level 2 [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Fair value financial assets measured on recurring basis | 185 | 310
Fixed-Maturity Investments [Member] | Taxable Bonds [Member] | Asset-Backed Securities [Member] | Other Asset-Backed [Member] | Fair Value, Inputs, Level 3 [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Fair value financial assets measured on recurring basis | 272 | 350
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 | 898 | 1,064
Fixed-Maturity Investments [Member] | Taxable Bonds [Member] | U.S. Treasury And Government Agency [Member] | Fair Value, Inputs, Level 1 [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Fair value financial assets measured on recurring basis | 749 | 915
Fixed-Maturity Investments [Member] | Taxable Bonds [Member] | U.S. Treasury And Government Agency [Member] | Fair Value, Inputs, Level 2 [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Fair value financial assets measured on recurring basis | 149 | 149
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 | 376 | 469
Fixed-Maturity Investments [Member] | Taxable Bonds [Member] | Foreign Governments [Member] | Fair Value, Inputs, Level 1 [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Fair value financial assets measured on recurring basis | 295 | 409
Fixed-Maturity Investments [Member] | Taxable Bonds [Member] | Foreign Governments [Member] | Fair Value, Inputs, Level 2 [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Fair value financial assets measured on recurring basis | 70 | 49
Fixed-Maturity Investments [Member] | Taxable Bonds [Member] | Foreign Governments [Member] | Fair Value, Inputs, Level 3 [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Fair value financial assets measured on recurring basis | 11 | 11
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 | 1,927 | 2,848
Fixed-Maturity Investments [Member] | Taxable Bonds [Member] | Corporate Obligations [Member] | Fair Value, Inputs, Level 1 [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Fair value financial assets measured on recurring basis | 1 |
Fixed-Maturity Investments [Member] | Taxable Bonds [Member] | Corporate Obligations [Member] | Fair Value, Inputs, Level 2 [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Fair value financial assets measured on recurring basis | 1,584 | 2,602
Fixed-Maturity Investments [Member] | Taxable Bonds [Member] | Corporate Obligations [Member] | Fair Value, Inputs, Level 3 [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Fair value financial assets measured on recurring basis | 342 | 246
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 | 852 | 752
Fixed-Maturity Investments [Member] | Taxable Bonds [Member] | State And Municipal Bonds [Member] | Fair Value, Inputs, Level 2 [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Fair value financial assets measured on recurring basis | 852 | 738
Fixed-Maturity Investments [Member] | Taxable Bonds [Member] | State And Municipal Bonds [Member] | Fair Value, Inputs, Level 3 [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Fair value financial assets measured on recurring basis |  | 14
Fixed-Maturity Investments [Member] | Taxable Bonds [Member] | Fair Value, Inputs, Level 1 [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Fair value financial assets measured on recurring basis | 1,045 | 1,324
Fixed-Maturity Investments [Member] | Taxable Bonds [Member] | Fair Value, Inputs, Level 2 [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Fair value financial assets measured on recurring basis | 4,799 | 6,038
Fixed-Maturity Investments [Member] | Taxable Bonds [Member] | Fair Value, Inputs, Level 3 [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Fair value financial assets measured on recurring basis | 750 | 942
Fixed-Maturity Investments [Member] | State And Municipal Taxable Bonds [Member] | Tax-Exempt Bonds [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Fair value financial assets measured on recurring basis | 2,845 | 2,823
Fixed-Maturity Investments [Member] | State And Municipal Taxable Bonds [Member] | Tax-Exempt Bonds [Member] | Fair Value, Inputs, Level 2 [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Fair value financial assets measured on recurring basis | 2,815 | 2,787
Fixed-Maturity Investments [Member] | State And Municipal Taxable Bonds [Member] | Tax-Exempt Bonds [Member] | Fair Value, Inputs, Level 3 [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Fair value financial assets measured on recurring basis | 30 | 36
Fixed-Maturity Investments [Member] | Fair Value, Inputs, Level 1 [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Fair value financial assets measured on recurring basis | 1,045 | 1,337
Fixed-Maturity Investments [Member] | Fair Value, Inputs, Level 2 [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Fair value financial assets measured on recurring basis | 7,629 | 8,844
Fixed-Maturity Investments [Member] | Fair Value, Inputs, Level 3 [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Fair value financial assets measured on recurring basis | 780 | 978
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 | 15 | 32
Fixed-Maturity Investments [Member] | Other-Fixed Maturity Investments [Member] | Fair Value, Inputs, Level 1 [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Fair value financial assets measured on recurring basis |  | 13
Fixed-Maturity Investments [Member] | Other-Fixed Maturity Investments [Member] | Fair Value, Inputs, Level 2 [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Fair value financial assets measured on recurring basis | 15 | 19
Other Long Term Investments [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Fair value financial assets measured on recurring basis |  | 21
Other Long Term Investments [Member] | Fair Value, Inputs, Level 1 [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Fair value financial assets measured on recurring basis |  | 16
Other Long Term Investments [Member] | Fair Value, Inputs, Level 2 [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Fair value financial assets measured on recurring basis |  | 5
Other Long Term Investments [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Fair value financial assets measured on recurring basis | 27 |
Other Long Term Investments [Member] | Fair Value, Inputs, Level 1 [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Fair value financial assets measured on recurring basis | 27 |
Derivative Assets [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Fair value financial assets measured on recurring basis | 2 | 4
Derivative Assets [Member] | Credit 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] | Non-Insured Derivatives [Member] | Fair Value, Inputs, Level 2 [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Fair value financial assets measured on recurring basis | 1 |
Derivative Assets [Member] | Credit Derivatives [Member] | Fair Value, Inputs, Level 2 [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Fair value financial assets measured on recurring basis |  | 3
Derivative Assets [Member] | Interest Rate Derivatives [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Fair value financial assets measured on recurring basis |  | 62
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 | 92 |
Derivative Assets [Member] | Interest Rate Derivatives [Member] | Non-Insured Derivatives [Member] | Fair Value, Inputs, Level 2 [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Fair value financial assets measured on recurring basis | 89 |
Derivative Assets [Member] | Interest Rate Derivatives [Member] | Non-Insured Derivatives [Member] | Fair Value, Inputs, Level 3 [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Fair value financial assets measured on recurring basis | 3 |
Derivative Assets [Member] | Interest Rate Derivatives [Member] | Fair Value, Inputs, Level 2 [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Fair value financial assets measured on recurring basis |  | 57
Derivative Assets [Member] | Interest Rate Derivatives [Member] | Fair Value, Inputs, Level 3 [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Fair value financial assets measured on recurring basis |  | 5
Derivative Assets [Member] | Other Derivatives [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Fair value financial assets measured on recurring basis |  | (61)
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 | (91) |
Derivative Assets [Member] | Other Derivatives [Member] | Non-Insured Derivatives [Member] | Counterparty And Cash Collateral Netting [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Fair value financial assets measured on recurring basis | (91) |
Derivative Assets [Member] | Other Derivatives [Member] | Counterparty And Cash Collateral Netting [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Fair value financial assets measured on recurring basis |  | (61)
Derivative Assets [Member] | Fair Value, Inputs, Level 2 [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Fair value financial assets measured on recurring basis | 90 | 60
Derivative Assets [Member] | Fair Value, Inputs, Level 3 [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Fair value financial assets measured on recurring basis | 3 | 5
Derivative Assets [Member] | Counterparty And Cash Collateral Netting [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Fair value financial assets measured on recurring basis | (91) | (61)
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 | 4,901 | 4,375
Derivative Liabilities [Member] | Credit Derivatives [Member] | Insured Derivatives [Member] | Fair Value, Inputs, Level 2 [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Fair value financial liabilities measured on recurring basis | 21 | 25
Derivative Liabilities [Member] | Credit Derivatives [Member] | Insured Derivatives [Member] | Fair Value, Inputs, Level 3 [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Fair value financial liabilities measured on recurring basis | 4,880 | 4,350
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 | 450 | 297
Derivative Liabilities [Member] | Interest Rate Derivatives [Member] | Non-Insured Derivatives [Member] | Fair Value, Inputs, Level 2 [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Fair value financial liabilities measured on recurring basis | 450 | 297
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 | 6 | 6
Derivative Liabilities [Member] | Currency Derivatives [Member] | Non-Insured Derivatives [Member] | Fair Value, Inputs, Level 2 [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Fair value financial liabilities measured on recurring basis | 6 | 6
Derivative Liabilities [Member] | Other Derivatives [Member] | Non-Insured Derivatives [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Fair value financial liabilities measured on recurring basis | (91) | (61)
Derivative Liabilities [Member] | Other Derivatives [Member] | Non-Insured Derivatives [Member] | Counterparty And Cash Collateral Netting [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Fair value financial liabilities measured on recurring basis | (91) | (61)
Other Liabilities [Member] | Warrants [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Fair value financial liabilities measured on recurring basis | 12 | 58
Other Liabilities [Member] | Warrants [Member] | Fair Value, Inputs, Level 2 [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Fair value financial liabilities measured on recurring basis | 12 | 58
Total Investments [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Fair value financial assets measured on recurring basis | 10,321 | 11,925
Total Investments [Member] | Fair Value, Inputs, Level 1 [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Fair value financial assets measured on recurring basis | 1,765 | 1,906
Total Investments [Member] | Fair Value, Inputs, Level 2 [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Fair value financial assets measured on recurring basis | 7,775 | 9,041
Total Investments [Member] | Fair Value, Inputs, Level 3 [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Fair value financial assets measured on recurring basis | 781 | 978
Perpetual Preferred Securities [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Fair value financial assets measured on recurring basis | 147 | 192
Perpetual Preferred Securities [Member] | Fair Value, Inputs, Level 2 [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Fair value financial assets measured on recurring basis | 146 | 192
Perpetual Preferred Securities [Member] | Fair Value, Inputs, Level 3 [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Fair value financial assets measured on recurring basis | 1 |
Money Market Securities [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Fair value financial assets measured on recurring basis | 693 | 553
Money Market Securities [Member] | Fair Value, Inputs, Level 1 [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Fair value financial assets measured on recurring basis | 693 | 553
Medium-Term Notes [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Fair value financial liabilities measured on recurring basis | 128 | 116
Medium-Term Notes [Member] | Fair Value, Inputs, Level 3 [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Fair value financial liabilities measured on recurring basis | 128 | 116
Fair Value, Inputs, Level 1 [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Fair value financial assets measured on recurring basis | 1,983 | 2,067
Fair Value, Inputs, Level 2 [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Fair value financial assets measured on recurring basis | 11,088 | 14,062
Fair value financial liabilities measured on recurring basis | 2,878 | 3,028
Fair Value, Inputs, Level 3 [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Fair value financial assets measured on recurring basis | 5,020 | 5,159
Fair value financial liabilities measured on recurring basis | 9,630 | 10,608
Counterparty And Cash Collateral Netting [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Fair value financial assets measured on recurring basis | (91) | (61)
Fair value financial liabilities measured on recurring basis | $ (91) | $ (61)

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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 Available-for-Sale Securities -URI http://asc.fasb.org/extlink&oid=6505594 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=6379932&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 FASB -Name Accounting Standards Codification -Glossary Trading Securities -URI http://asc.fasb.org/extlink&oid=6526789 Reference 5: 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 6: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Article 7 -Section 03 -Paragraph 1 -Subparagraph a, f, g 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=6956420&loc=d3e24584-111560 + Details
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