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Fair Value Of Financial Instruments (Company's Assets And Liabilities Measured At Fair Value On Recurring Basis) (Detail) - Fair Value Measurements Recurring [Member] - USD ($)
$ in Millions
Mar. 31, 2021
Dec. 31, 2020
Accounts Notes And Loans Receivable [Line Items]    
Fair value financial assets measured on recurring basis $ 3,397 $ 3,725
Fair value financial liabilities measured on recurring basis 556 675
Money Market Securities [Member]    
Accounts Notes And Loans Receivable [Line Items]    
Fair value financial assets measured on recurring basis 30 1
Medium-term Notes [Member]    
Accounts Notes And Loans Receivable [Line Items]    
Fair value financial liabilities measured on recurring basis 105 110
Perpetual Debt And Equity Securities [Member]    
Accounts Notes And Loans Receivable [Line Items]    
Fair value financial assets measured on recurring basis 64 62
Cash and Cash Equivalents [Member]    
Accounts Notes And Loans Receivable [Line Items]    
Fair value financial assets measured on recurring basis 116 158
Fixed Maturities [Member]    
Accounts Notes And Loans Receivable [Line Items]    
Fair value financial assets measured on recurring basis 2,958 2,673
Fixed Maturities [Member] | U S Treasury And Government [Member] | Other Fixed Maturity Investments [Member]    
Accounts Notes And Loans Receivable [Line Items]    
Fair value financial assets measured on recurring basis 1,054 855
Fixed Maturities [Member] | State and municipal bonds [Member] | Other Fixed Maturity Investments [Member]    
Accounts Notes And Loans Receivable [Line Items]    
Fair value financial assets measured on recurring basis 185 195
Fixed Maturities [Member] | Foreign Government Debt [Member] | Other Fixed Maturity Investments [Member]    
Accounts Notes And Loans Receivable [Line Items]    
Fair value financial assets measured on recurring basis 17 15
Fixed Maturities [Member] | Corporate Obligations [Member] | Other Fixed Maturity Investments [Member]    
Accounts Notes And Loans Receivable [Line Items]    
Fair value financial assets measured on recurring basis 984 975
Fixed Maturities [Member] | Residential Mortgage Backed Agency [Member] | Mortgage-backed [Member]    
Accounts Notes And Loans Receivable [Line Items]    
Fair value financial assets measured on recurring basis 296 319
Fixed Maturities [Member] | Residential Mortgage Backed Non Agency [Member] | Mortgage-backed [Member]    
Accounts Notes And Loans Receivable [Line Items]    
Fair value financial assets measured on recurring basis 90 32
Fixed Maturities [Member] | Commercial Mortgage Backed Securities [Member] | Mortgage-backed [Member]    
Accounts Notes And Loans Receivable [Line Items]    
Fair value financial assets measured on recurring basis 14 20
Fixed Maturities [Member] | Collateralized Debt Obligations [Member] | Asset-backed [Member]    
Accounts Notes And Loans Receivable [Line Items]    
Fair value financial assets measured on recurring basis 125 121
Fixed Maturities [Member] | Other Asset Backed [Member] | Asset-backed [Member]    
Accounts Notes And Loans Receivable [Line Items]    
Fair value financial assets measured on recurring basis 193 141
Derivative Assets [Member] | Interest Rate Derivatives [Member] | Non-Insured Derivatives [Member]    
Accounts Notes And Loans Receivable [Line Items]    
Fair value financial assets measured on recurring basis 1 1
Assets Of Consolidated V I Es [Member] | Variable Interest Entity, Primary Beneficiary [Member] | Loan Repurchase Commitments [Member]    
Accounts Notes And Loans Receivable [Line Items]    
Fair value financial assets measured on recurring basis   604
Assets Of Consolidated V I Es [Member] | Corporate Obligations [Member] | Variable Interest Entity, Primary Beneficiary [Member]    
Accounts Notes And Loans Receivable [Line Items]    
Fair value financial assets measured on recurring basis 6 6
Assets Of Consolidated V I Es [Member] | Residential Mortgage Backed Non Agency [Member] | Mortgage-backed [Member] | Variable Interest Entity, Primary Beneficiary [Member]    
Accounts Notes And Loans Receivable [Line Items]    
Fair value financial assets measured on recurring basis 38 40
Assets Of Consolidated V I Es [Member] | Commercial Mortgage Backed Securities [Member] | Mortgage-backed [Member] | Variable Interest Entity, Primary Beneficiary [Member]    
Accounts Notes And Loans Receivable [Line Items]    
Fair value financial assets measured on recurring basis 16 16
Assets Of Consolidated V I Es [Member] | Collateralized Debt Obligations [Member] | Asset-backed [Member] | Variable Interest Entity, Primary Beneficiary [Member]    
Accounts Notes And Loans Receivable [Line Items]    
Fair value financial assets measured on recurring basis 8 8
Assets Of Consolidated V I Es [Member] | Other Asset Backed [Member] | Asset-backed [Member] | Variable Interest Entity, Primary Beneficiary [Member]    
Accounts Notes And Loans Receivable [Line Items]    
Fair value financial assets measured on recurring basis 8 7
Assets Of Consolidated V I Es [Member] | Loans Receivable and Other Instruments At Fair Value [Member] | Variable Interest Entity, Primary Beneficiary [Member] | Residential Loans Receivable [Member]    
Accounts Notes And Loans Receivable [Line Items]    
Fair value financial assets measured on recurring basis 124 120
Assets Of Consolidated V I Es [Member] | Currency Derivatives [Member] | Variable Interest Entity, Primary Beneficiary [Member]    
Accounts Notes And Loans Receivable [Line Items]    
Fair value financial assets measured on recurring basis 9 6
Assets Of Consolidated V I Es [Member] | Cash and Cash Equivalents [Member] | Variable Interest Entity, Primary Beneficiary [Member]    
Accounts Notes And Loans Receivable [Line Items]    
Fair value financial assets measured on recurring basis 5 9
Assets Of Consolidated V I Es [Member] | Other [Member] | Variable Interest Entity, Primary Beneficiary [Member]    
Accounts Notes And Loans Receivable [Line Items]    
Fair value financial assets measured on recurring basis 14 14
Derivative Liabilities [Member] | Credit Derivatives [Member] | Insured Derivatives [Member]    
Accounts Notes And Loans Receivable [Line Items]    
Fair value financial liabilities measured on recurring basis 1 2
Derivative Liabilities [Member] | Interest Rate Derivatives [Member] | Non-Insured Derivatives [Member]    
Accounts Notes And Loans Receivable [Line Items]    
Fair value financial liabilities measured on recurring basis 125 164
Derivative Liabilities [Member] | Other Derivatives [Member] | Non-Insured Derivatives [Member]    
Accounts Notes And Loans Receivable [Line Items]    
Fair value financial liabilities measured on recurring basis   49
Liabilities Of Consolidated Vies [Member] | Variable Interest Entity Notes [Member] | Variable Interest Entity, Primary Beneficiary [Member]    
Accounts Notes And Loans Receivable [Line Items]    
Fair value financial liabilities measured on recurring basis 325 350
Fair Value Inputs Level 1 [Member]    
Accounts Notes And Loans Receivable [Line Items]    
Fair value financial assets measured on recurring basis 1,146 955
Fair value financial liabilities measured on recurring basis 0 0
Fair Value Inputs Level 1 [Member] | Money Market Securities [Member]    
Accounts Notes And Loans Receivable [Line Items]    
Fair value financial assets measured on recurring basis 30 1
Fair Value Inputs Level 1 [Member] | Medium-term Notes [Member]    
Accounts Notes And Loans Receivable [Line Items]    
Fair value financial liabilities measured on recurring basis 0 0
Fair Value Inputs Level 1 [Member] | Perpetual Debt And Equity Securities [Member]    
Accounts Notes And Loans Receivable [Line Items]    
Fair value financial assets measured on recurring basis 40 37
Fair Value Inputs Level 1 [Member] | Cash and Cash Equivalents [Member]    
Accounts Notes And Loans Receivable [Line Items]    
Fair value financial assets measured on recurring basis 116 158
Fair Value Inputs Level 1 [Member] | Fixed Maturities [Member]    
Accounts Notes And Loans Receivable [Line Items]    
Fair value financial assets measured on recurring basis 955 750
Fair Value Inputs Level 1 [Member] | Fixed Maturities [Member] | U S Treasury And Government [Member] | Other Fixed Maturity Investments [Member]    
Accounts Notes And Loans Receivable [Line Items]    
Fair value financial assets measured on recurring basis 955 750
Fair Value Inputs Level 1 [Member] | Fixed Maturities [Member] | State and municipal bonds [Member] | Other Fixed Maturity Investments [Member]    
Accounts Notes And Loans Receivable [Line Items]    
Fair value financial assets measured on recurring basis 0 0
Fair Value Inputs Level 1 [Member] | Fixed Maturities [Member] | Foreign Government Debt [Member] | Other Fixed Maturity Investments [Member]    
Accounts Notes And Loans Receivable [Line Items]    
Fair value financial assets measured on recurring basis 0 0
Fair Value Inputs Level 1 [Member] | Fixed Maturities [Member] | Corporate Obligations [Member] | Other Fixed Maturity Investments [Member]    
Accounts Notes And Loans Receivable [Line Items]    
Fair value financial assets measured on recurring basis 0 0
Fair Value Inputs Level 1 [Member] | Fixed Maturities [Member] | Residential Mortgage Backed Agency [Member] | Mortgage-backed [Member]    
Accounts Notes And Loans Receivable [Line Items]    
Fair value financial assets measured on recurring basis 0 0
Fair Value Inputs Level 1 [Member] | Fixed Maturities [Member] | Residential Mortgage Backed Non Agency [Member] | Mortgage-backed [Member]    
Accounts Notes And Loans Receivable [Line Items]    
Fair value financial assets measured on recurring basis 0 0
Fair Value Inputs Level 1 [Member] | Fixed Maturities [Member] | Commercial Mortgage Backed Securities [Member] | Mortgage-backed [Member]    
Accounts Notes And Loans Receivable [Line Items]    
Fair value financial assets measured on recurring basis 0 0
Fair Value Inputs Level 1 [Member] | Fixed Maturities [Member] | Collateralized Debt Obligations [Member] | Asset-backed [Member]    
Accounts Notes And Loans Receivable [Line Items]    
Fair value financial assets measured on recurring basis 0 0
Fair Value Inputs Level 1 [Member] | Fixed Maturities [Member] | Other Asset Backed [Member] | Asset-backed [Member]    
Accounts Notes And Loans Receivable [Line Items]    
Fair value financial assets measured on recurring basis 0 0
Fair Value Inputs Level 1 [Member] | Derivative Assets [Member] | Interest Rate Derivatives [Member] | Non-Insured Derivatives [Member]    
Accounts Notes And Loans Receivable [Line Items]    
Fair value financial assets measured on recurring basis 0 0
Fair Value Inputs Level 1 [Member] | Assets Of Consolidated V I Es [Member] | Variable Interest Entity, Primary Beneficiary [Member] | Loan Repurchase Commitments [Member]    
Accounts Notes And Loans Receivable [Line Items]    
Fair value financial assets measured on recurring basis   0
Fair Value Inputs Level 1 [Member] | Assets Of Consolidated V I Es [Member] | Corporate Obligations [Member] | Variable Interest Entity, Primary Beneficiary [Member]    
Accounts Notes And Loans Receivable [Line Items]    
Fair value financial assets measured on recurring basis 0 0
Fair Value Inputs Level 1 [Member] | Assets Of Consolidated V I Es [Member] | Residential Mortgage Backed Non Agency [Member] | Mortgage-backed [Member] | Variable Interest Entity, Primary Beneficiary [Member]    
Accounts Notes And Loans Receivable [Line Items]    
Fair value financial assets measured on recurring basis 0 0
Fair Value Inputs Level 1 [Member] | Assets Of Consolidated V I Es [Member] | Commercial Mortgage Backed Securities [Member] | Mortgage-backed [Member] | Variable Interest Entity, Primary Beneficiary [Member]    
Accounts Notes And Loans Receivable [Line Items]    
Fair value financial assets measured on recurring basis 0 0
Fair Value Inputs Level 1 [Member] | Assets Of Consolidated V I Es [Member] | Collateralized Debt Obligations [Member] | Asset-backed [Member] | Variable Interest Entity, Primary Beneficiary [Member]    
Accounts Notes And Loans Receivable [Line Items]    
Fair value financial assets measured on recurring basis 0 0
Fair Value Inputs Level 1 [Member] | Assets Of Consolidated V I Es [Member] | Other Asset Backed [Member] | Asset-backed [Member] | Variable Interest Entity, Primary Beneficiary [Member]    
Accounts Notes And Loans Receivable [Line Items]    
Fair value financial assets measured on recurring basis 0 0
Fair Value Inputs Level 1 [Member] | Assets Of Consolidated V I Es [Member] | Loans Receivable and Other Instruments At Fair Value [Member] | Variable Interest Entity, Primary Beneficiary [Member] | Residential Loans Receivable [Member]    
Accounts Notes And Loans Receivable [Line Items]    
Fair value financial assets measured on recurring basis 0 0
Fair Value Inputs Level 1 [Member] | Assets Of Consolidated V I Es [Member] | Currency Derivatives [Member] | Variable Interest Entity, Primary Beneficiary [Member]    
Accounts Notes And Loans Receivable [Line Items]    
Fair value financial assets measured on recurring basis 0 0
Fair Value Inputs Level 1 [Member] | Assets Of Consolidated V I Es [Member] | Cash and Cash Equivalents [Member] | Variable Interest Entity, Primary Beneficiary [Member]    
Accounts Notes And Loans Receivable [Line Items]    
Fair value financial assets measured on recurring basis 5 9
Fair Value Inputs Level 1 [Member] | Assets Of Consolidated V I Es [Member] | Other [Member] | Variable Interest Entity, Primary Beneficiary [Member]    
Accounts Notes And Loans Receivable [Line Items]    
Fair value financial assets measured on recurring basis 0 0
Fair Value Inputs Level 1 [Member] | Derivative Liabilities [Member] | Credit Derivatives [Member] | Insured Derivatives [Member]    
Accounts Notes And Loans Receivable [Line Items]    
Fair value financial liabilities measured on recurring basis 0 0
Fair Value Inputs Level 1 [Member] | Derivative Liabilities [Member] | Interest Rate Derivatives [Member] | Non-Insured Derivatives [Member]    
Accounts Notes And Loans Receivable [Line Items]    
Fair value financial liabilities measured on recurring basis 0 0
Fair Value Inputs Level 1 [Member] | Derivative Liabilities [Member] | Other Derivatives [Member] | Non-Insured Derivatives [Member]    
Accounts Notes And Loans Receivable [Line Items]    
Fair value financial liabilities measured on recurring basis   0
Fair Value Inputs Level 1 [Member] | Liabilities Of Consolidated Vies [Member] | Variable Interest Entity Notes [Member] | Variable Interest Entity, Primary Beneficiary [Member]    
Accounts Notes And Loans Receivable [Line Items]    
Fair value financial liabilities measured on recurring basis 0 0
Fair Value Inputs Level 2 [Member]    
Accounts Notes And Loans Receivable [Line Items]    
Fair value financial assets measured on recurring basis 2,104 2,026
Fair value financial liabilities measured on recurring basis 171 213
Fair Value Inputs Level 2 [Member] | Money Market Securities [Member]    
Accounts Notes And Loans Receivable [Line Items]    
Fair value financial assets measured on recurring basis 0 0
Fair Value Inputs Level 2 [Member] | Medium-term Notes [Member]    
Accounts Notes And Loans Receivable [Line Items]    
Fair value financial liabilities measured on recurring basis 0 0
Fair Value Inputs Level 2 [Member] | Perpetual Debt And Equity Securities [Member]    
Accounts Notes And Loans Receivable [Line Items]    
Fair value financial assets measured on recurring basis 24 25
Fair Value Inputs Level 2 [Member] | Cash and Cash Equivalents [Member]    
Accounts Notes And Loans Receivable [Line Items]    
Fair value financial assets measured on recurring basis 0 0
Fair Value Inputs Level 2 [Member] | Fixed Maturities [Member]    
Accounts Notes And Loans Receivable [Line Items]    
Fair value financial assets measured on recurring basis 2,003 1,923
Fair Value Inputs Level 2 [Member] | Fixed Maturities [Member] | U S Treasury And Government [Member] | Other Fixed Maturity Investments [Member]    
Accounts Notes And Loans Receivable [Line Items]    
Fair value financial assets measured on recurring basis 99 105
Fair Value Inputs Level 2 [Member] | Fixed Maturities [Member] | State and municipal bonds [Member] | Other Fixed Maturity Investments [Member]    
Accounts Notes And Loans Receivable [Line Items]    
Fair value financial assets measured on recurring basis 185 195
Fair Value Inputs Level 2 [Member] | Fixed Maturities [Member] | Foreign Government Debt [Member] | Other Fixed Maturity Investments [Member]    
Accounts Notes And Loans Receivable [Line Items]    
Fair value financial assets measured on recurring basis 17 15
Fair Value Inputs Level 2 [Member] | Fixed Maturities [Member] | Corporate Obligations [Member] | Other Fixed Maturity Investments [Member]    
Accounts Notes And Loans Receivable [Line Items]    
Fair value financial assets measured on recurring basis 984 975
Fair Value Inputs Level 2 [Member] | Fixed Maturities [Member] | Residential Mortgage Backed Agency [Member] | Mortgage-backed [Member]    
Accounts Notes And Loans Receivable [Line Items]    
Fair value financial assets measured on recurring basis 296 319
Fair Value Inputs Level 2 [Member] | Fixed Maturities [Member] | Residential Mortgage Backed Non Agency [Member] | Mortgage-backed [Member]    
Accounts Notes And Loans Receivable [Line Items]    
Fair value financial assets measured on recurring basis 90 32
Fair Value Inputs Level 2 [Member] | Fixed Maturities [Member] | Commercial Mortgage Backed Securities [Member] | Mortgage-backed [Member]    
Accounts Notes And Loans Receivable [Line Items]    
Fair value financial assets measured on recurring basis 14 20
Fair Value Inputs Level 2 [Member] | Fixed Maturities [Member] | Collateralized Debt Obligations [Member] | Asset-backed [Member]    
Accounts Notes And Loans Receivable [Line Items]    
Fair value financial assets measured on recurring basis 125 121
Fair Value Inputs Level 2 [Member] | Fixed Maturities [Member] | Other Asset Backed [Member] | Asset-backed [Member]    
Accounts Notes And Loans Receivable [Line Items]    
Fair value financial assets measured on recurring basis 193 141
Fair Value Inputs Level 2 [Member] | Derivative Assets [Member] | Interest Rate Derivatives [Member] | Non-Insured Derivatives [Member]    
Accounts Notes And Loans Receivable [Line Items]    
Fair value financial assets measured on recurring basis 1 1
Fair Value Inputs Level 2 [Member] | Assets Of Consolidated V I Es [Member] | Variable Interest Entity, Primary Beneficiary [Member] | Loan Repurchase Commitments [Member]    
Accounts Notes And Loans Receivable [Line Items]    
Fair value financial assets measured on recurring basis   0
Fair Value Inputs Level 2 [Member] | Assets Of Consolidated V I Es [Member] | Corporate Obligations [Member] | Variable Interest Entity, Primary Beneficiary [Member]    
Accounts Notes And Loans Receivable [Line Items]    
Fair value financial assets measured on recurring basis 6 6
Fair Value Inputs Level 2 [Member] | Assets Of Consolidated V I Es [Member] | Residential Mortgage Backed Non Agency [Member] | Mortgage-backed [Member] | Variable Interest Entity, Primary Beneficiary [Member]    
Accounts Notes And Loans Receivable [Line Items]    
Fair value financial assets measured on recurring basis 38 40
Fair Value Inputs Level 2 [Member] | Assets Of Consolidated V I Es [Member] | Commercial Mortgage Backed Securities [Member] | Mortgage-backed [Member] | Variable Interest Entity, Primary Beneficiary [Member]    
Accounts Notes And Loans Receivable [Line Items]    
Fair value financial assets measured on recurring basis 16 16
Fair Value Inputs Level 2 [Member] | Assets Of Consolidated V I Es [Member] | Collateralized Debt Obligations [Member] | Asset-backed [Member] | Variable Interest Entity, Primary Beneficiary [Member]    
Accounts Notes And Loans Receivable [Line Items]    
Fair value financial assets measured on recurring basis 8 8
Fair Value Inputs Level 2 [Member] | Assets Of Consolidated V I Es [Member] | Other Asset Backed [Member] | Asset-backed [Member] | Variable Interest Entity, Primary Beneficiary [Member]    
Accounts Notes And Loans Receivable [Line Items]    
Fair value financial assets measured on recurring basis 8 7
Fair Value Inputs Level 2 [Member] | Assets Of Consolidated V I Es [Member] | Loans Receivable and Other Instruments At Fair Value [Member] | Variable Interest Entity, Primary Beneficiary [Member] | Residential Loans Receivable [Member]    
Accounts Notes And Loans Receivable [Line Items]    
Fair value financial assets measured on recurring basis 0 0
Fair Value Inputs Level 2 [Member] | Assets Of Consolidated V I Es [Member] | Currency Derivatives [Member] | Variable Interest Entity, Primary Beneficiary [Member]    
Accounts Notes And Loans Receivable [Line Items]    
Fair value financial assets measured on recurring basis 0 0
Fair Value Inputs Level 2 [Member] | Assets Of Consolidated V I Es [Member] | Cash and Cash Equivalents [Member] | Variable Interest Entity, Primary Beneficiary [Member]    
Accounts Notes And Loans Receivable [Line Items]    
Fair value financial assets measured on recurring basis 0 0
Fair Value Inputs Level 2 [Member] | Assets Of Consolidated V I Es [Member] | Other [Member] | Variable Interest Entity, Primary Beneficiary [Member]    
Accounts Notes And Loans Receivable [Line Items]    
Fair value financial assets measured on recurring basis 0 0
Fair Value Inputs Level 2 [Member] | Derivative Liabilities [Member] | Credit Derivatives [Member] | Insured Derivatives [Member]    
Accounts Notes And Loans Receivable [Line Items]    
Fair value financial liabilities measured on recurring basis 1 2
Fair Value Inputs Level 2 [Member] | Derivative Liabilities [Member] | Interest Rate Derivatives [Member] | Non-Insured Derivatives [Member]    
Accounts Notes And Loans Receivable [Line Items]    
Fair value financial liabilities measured on recurring basis 125 164
Fair Value Inputs Level 2 [Member] | Derivative Liabilities [Member] | Other Derivatives [Member] | Non-Insured Derivatives [Member]    
Accounts Notes And Loans Receivable [Line Items]    
Fair value financial liabilities measured on recurring basis   0
Fair Value Inputs Level 2 [Member] | Liabilities Of Consolidated Vies [Member] | Variable Interest Entity Notes [Member] | Variable Interest Entity, Primary Beneficiary [Member]    
Accounts Notes And Loans Receivable [Line Items]    
Fair value financial liabilities measured on recurring basis 45 47
Fair Value Inputs Level 3 [Member]    
Accounts Notes And Loans Receivable [Line Items]    
Fair value financial assets measured on recurring basis 147 744
Fair value financial liabilities measured on recurring basis 385 462
Fair Value Inputs Level 3 [Member] | Money Market Securities [Member]    
Accounts Notes And Loans Receivable [Line Items]    
Fair value financial assets measured on recurring basis 0 0
Fair Value Inputs Level 3 [Member] | Medium-term Notes [Member]    
Accounts Notes And Loans Receivable [Line Items]    
Fair value financial liabilities measured on recurring basis 105 110
Fair Value Inputs Level 3 [Member] | Perpetual Debt And Equity Securities [Member]    
Accounts Notes And Loans Receivable [Line Items]    
Fair value financial assets measured on recurring basis 0 0
Fair Value Inputs Level 3 [Member] | Cash and Cash Equivalents [Member]    
Accounts Notes And Loans Receivable [Line Items]    
Fair value financial assets measured on recurring basis 0 0
Fair Value Inputs Level 3 [Member] | Fixed Maturities [Member]    
Accounts Notes And Loans Receivable [Line Items]    
Fair value financial assets measured on recurring basis 0 0
Fair Value Inputs Level 3 [Member] | Fixed Maturities [Member] | U S Treasury And Government [Member] | Other Fixed Maturity Investments [Member]    
Accounts Notes And Loans Receivable [Line Items]    
Fair value financial assets measured on recurring basis 0 0
Fair Value Inputs Level 3 [Member] | Fixed Maturities [Member] | State and municipal bonds [Member] | Other Fixed Maturity Investments [Member]    
Accounts Notes And Loans Receivable [Line Items]    
Fair value financial assets measured on recurring basis 0 0
Fair Value Inputs Level 3 [Member] | Fixed Maturities [Member] | Foreign Government Debt [Member] | Other Fixed Maturity Investments [Member]    
Accounts Notes And Loans Receivable [Line Items]    
Fair value financial assets measured on recurring basis 0 0
Fair Value Inputs Level 3 [Member] | Fixed Maturities [Member] | Corporate Obligations [Member] | Other Fixed Maturity Investments [Member]    
Accounts Notes And Loans Receivable [Line Items]    
Fair value financial assets measured on recurring basis 0 0
Fair Value Inputs Level 3 [Member] | Fixed Maturities [Member] | Residential Mortgage Backed Agency [Member] | Mortgage-backed [Member]    
Accounts Notes And Loans Receivable [Line Items]    
Fair value financial assets measured on recurring basis 0 0
Fair Value Inputs Level 3 [Member] | Fixed Maturities [Member] | Residential Mortgage Backed Non Agency [Member] | Mortgage-backed [Member]    
Accounts Notes And Loans Receivable [Line Items]    
Fair value financial assets measured on recurring basis 0 0
Fair Value Inputs Level 3 [Member] | Fixed Maturities [Member] | Commercial Mortgage Backed Securities [Member] | Mortgage-backed [Member]    
Accounts Notes And Loans Receivable [Line Items]    
Fair value financial assets measured on recurring basis 0 0
Fair Value Inputs Level 3 [Member] | Fixed Maturities [Member] | Collateralized Debt Obligations [Member] | Asset-backed [Member]    
Accounts Notes And Loans Receivable [Line Items]    
Fair value financial assets measured on recurring basis 0 0
Fair Value Inputs Level 3 [Member] | Fixed Maturities [Member] | Other Asset Backed [Member] | Asset-backed [Member]    
Accounts Notes And Loans Receivable [Line Items]    
Fair value financial assets measured on recurring basis 0 0
Fair Value Inputs Level 3 [Member] | Derivative Assets [Member] | Interest Rate Derivatives [Member] | Non-Insured Derivatives [Member]    
Accounts Notes And Loans Receivable [Line Items]    
Fair value financial assets measured on recurring basis 0 0
Fair Value Inputs Level 3 [Member] | Assets Of Consolidated V I Es [Member] | Variable Interest Entity, Primary Beneficiary [Member] | Loan Repurchase Commitments [Member]    
Accounts Notes And Loans Receivable [Line Items]    
Fair value financial assets measured on recurring basis   604
Fair Value Inputs Level 3 [Member] | Assets Of Consolidated V I Es [Member] | Corporate Obligations [Member] | Variable Interest Entity, Primary Beneficiary [Member]    
Accounts Notes And Loans Receivable [Line Items]    
Fair value financial assets measured on recurring basis 0 0
Fair Value Inputs Level 3 [Member] | Assets Of Consolidated V I Es [Member] | Residential Mortgage Backed Non Agency [Member] | Mortgage-backed [Member] | Variable Interest Entity, Primary Beneficiary [Member]    
Accounts Notes And Loans Receivable [Line Items]    
Fair value financial assets measured on recurring basis 0 0
Fair Value Inputs Level 3 [Member] | Assets Of Consolidated V I Es [Member] | Commercial Mortgage Backed Securities [Member] | Mortgage-backed [Member] | Variable Interest Entity, Primary Beneficiary [Member]    
Accounts Notes And Loans Receivable [Line Items]    
Fair value financial assets measured on recurring basis 0 0
Fair Value Inputs Level 3 [Member] | Assets Of Consolidated V I Es [Member] | Collateralized Debt Obligations [Member] | Asset-backed [Member] | Variable Interest Entity, Primary Beneficiary [Member]    
Accounts Notes And Loans Receivable [Line Items]    
Fair value financial assets measured on recurring basis 0 0
Fair Value Inputs Level 3 [Member] | Assets Of Consolidated V I Es [Member] | Other Asset Backed [Member] | Asset-backed [Member] | Variable Interest Entity, Primary Beneficiary [Member]    
Accounts Notes And Loans Receivable [Line Items]    
Fair value financial assets measured on recurring basis 0 0
Fair Value Inputs Level 3 [Member] | Assets Of Consolidated V I Es [Member] | Loans Receivable and Other Instruments At Fair Value [Member] | Variable Interest Entity, Primary Beneficiary [Member] | Residential Loans Receivable [Member]    
Accounts Notes And Loans Receivable [Line Items]    
Fair value financial assets measured on recurring basis 124 120
Fair Value Inputs Level 3 [Member] | Assets Of Consolidated V I Es [Member] | Currency Derivatives [Member] | Variable Interest Entity, Primary Beneficiary [Member]    
Accounts Notes And Loans Receivable [Line Items]    
Fair value financial assets measured on recurring basis 9 6
Fair Value Inputs Level 3 [Member] | Assets Of Consolidated V I Es [Member] | Cash and Cash Equivalents [Member] | Variable Interest Entity, Primary Beneficiary [Member]    
Accounts Notes And Loans Receivable [Line Items]    
Fair value financial assets measured on recurring basis 0 0
Fair Value Inputs Level 3 [Member] | Assets Of Consolidated V I Es [Member] | Other [Member] | Variable Interest Entity, Primary Beneficiary [Member]    
Accounts Notes And Loans Receivable [Line Items]    
Fair value financial assets measured on recurring basis 14 14
Fair Value Inputs Level 3 [Member] | Derivative Liabilities [Member] | Credit Derivatives [Member] | Insured Derivatives [Member]    
Accounts Notes And Loans Receivable [Line Items]    
Fair value financial liabilities measured on recurring basis 0 0
Fair Value Inputs Level 3 [Member] | Derivative Liabilities [Member] | Interest Rate Derivatives [Member] | Non-Insured Derivatives [Member]    
Accounts Notes And Loans Receivable [Line Items]    
Fair value financial liabilities measured on recurring basis 0 0
Fair Value Inputs Level 3 [Member] | Derivative Liabilities [Member] | Other Derivatives [Member] | Non-Insured Derivatives [Member]    
Accounts Notes And Loans Receivable [Line Items]    
Fair value financial liabilities measured on recurring basis   49
Fair Value Inputs Level 3 [Member] | Liabilities Of Consolidated Vies [Member] | Variable Interest Entity Notes [Member] | Variable Interest Entity, Primary Beneficiary [Member]    
Accounts Notes And Loans Receivable [Line Items]    
Fair value financial liabilities measured on recurring basis $ 280 $ 303