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Fair Value Of Financial Instruments (Quantitative Information Regarding The Significant Unobservable Inputs For Certain Assets And Liabilities Measured At Fair Value On A Recurring Basis) (Detail) - USD ($) $ in Millions | Jun. 30, 2019 | Dec. 31, 2018
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Cash Flows [Member] | Other Derivatives Liabilities [Member] | Discounted cash flow [Member] |  |  |  |
Fair Value Assets Measured On Recurring Basis Unobservable Input Reconciliation [Line Items] |  |  |  |
Fair value, liabilities |  | $ 16 |  | $ 7
Cash Flows [Member] | Other Derivatives Liabilities [Member] | Minimum [Member] | Discounted cash flow [Member] |  |  |  |
Fair Value Assets Measured On Recurring Basis Unobservable Input Reconciliation [Line Items] |  |  |  |
Range dollars |  | 0 |  | 0
Cash Flows [Member] | Other Derivatives Liabilities [Member] | Maximum [Member] | Discounted cash flow [Member] |  |  |  |
Fair Value Assets Measured On Recurring Basis Unobservable Input Reconciliation [Line Items] |  |  |  |
Range dollars |  | 49 |  | 49
Cash Flows [Member] | Other Derivatives Liabilities [Member] | Weighted Average [Member] | Discounted cash flow [Member] |  |  |  |
Fair Value Assets Measured On Recurring Basis Unobservable Input Reconciliation [Line Items] |  |  |  |
Range dollars | [1] | 25 |  | 25
Credit Derivatives [Member] | Nonperformance Risk [Member] | Commercial Mortgage Backed Securities [Member] | Direct Price Model [Member] |  |  |  |
Fair Value Assets Measured On Recurring Basis Unobservable Input Reconciliation [Line Items] |  |  |  |
Fair value, liabilities |  | $ 18 |  | $ 33
Credit Derivatives [Member] | Nonperformance Risk [Member] | Commercial Mortgage Backed Securities [Member] | Minimum [Member] | Direct Price Model [Member] |  |  |  |
Fair Value Assets Measured On Recurring Basis Unobservable Input Reconciliation [Line Items] |  |  |  |
Range percentage |  | 54.00% |  | 54.00%
Credit Derivatives [Member] | Nonperformance Risk [Member] | Commercial Mortgage Backed Securities [Member] | Maximum [Member] | Direct Price Model [Member] |  |  |  |
Fair Value Assets Measured On Recurring Basis Unobservable Input Reconciliation [Line Items] |  |  |  |
Range percentage |  | 54.00% |  | 54.00%
Credit Derivatives [Member] | Nonperformance Risk [Member] | Commercial Mortgage Backed Securities [Member] | Weighted Average [Member] | Direct Price Model [Member] |  |  |  |
Fair Value Assets Measured On Recurring Basis Unobservable Input Reconciliation [Line Items] |  |  |  |
Range percentage |  | 54.00% |  | 54.00%
Loans Receivable and Other Instruments at Fair Value [Member] | Variable Interest Entity Primary Beneficiary [Member] | Impact Of Financial Guarantee [Member] | Market Prices Adjusted For Financial Guarantees Provided To Vie Obligations [Member] |  |  |  |
Fair Value Assets Measured On Recurring Basis Unobservable Input Reconciliation [Line Items] |  |  |  |
Fair Value, assets |  | $ 154 |  | $ 172
Loans Receivable and Other Instruments at Fair Value [Member] | Variable Interest Entity Primary Beneficiary [Member] | Impact Of Financial Guarantee [Member] | Minimum [Member] | Market Prices Adjusted For Financial Guarantees Provided To Vie Obligations [Member] |  |  |  |
Fair Value Assets Measured On Recurring Basis Unobservable Input Reconciliation [Line Items] |  |  |  |
Range percentage |  | (10.00%) |  | (17.00%)
Loans Receivable and Other Instruments at Fair Value [Member] | Variable Interest Entity Primary Beneficiary [Member] | Impact Of Financial Guarantee [Member] | Maximum [Member] | Market Prices Adjusted For Financial Guarantees Provided To Vie Obligations [Member] |  |  |  |
Fair Value Assets Measured On Recurring Basis Unobservable Input Reconciliation [Line Items] |  |  |  |
Range percentage |  | 59.00% | [2] | 75.00%
Loans Receivable and Other Instruments at Fair Value [Member] | Variable Interest Entity Primary Beneficiary [Member] | Impact Of Financial Guarantee [Member] | Weighted Average [Member] | Market Prices Adjusted For Financial Guarantees Provided To Vie Obligations [Member] |  |  |  |
Fair Value Assets Measured On Recurring Basis Unobservable Input Reconciliation [Line Items] |  |  |  |
Range percentage |  | 16.00% |  | 7.00%
Loan Repurchase Commitments [Member] | Variable Interest Entity Primary Beneficiary [Member] | Recovery Rates And Breach Rates [Member] | Discounted cash flow [Member] |  |  |  |
Fair Value Assets Measured On Recurring Basis Unobservable Input Reconciliation [Line Items] |  |  |  |
Fair Value, assets |  | $ 428 |  | $ 418
Variable Interest Entity Notes [Member] | Variable Interest Entity Primary Beneficiary [Member] | Impact Of Financial Guarantee [Member] | Quoted market prices of VIE assets adjusted for financial guarantees provided [Member] |  |  |  |
Fair Value Assets Measured On Recurring Basis Unobservable Input Reconciliation [Line Items] |  |  |  |
Fair value, liabilities |  | $ 342 |  | $ 366
Variable Interest Entity Notes [Member] | Variable Interest Entity Primary Beneficiary [Member] | Impact Of Financial Guarantee [Member] | Minimum [Member] | Quoted market prices of VIE assets adjusted for financial guarantees provided [Member] |  |  |  |
Fair Value Assets Measured On Recurring Basis Unobservable Input Reconciliation [Line Items] |  |  |  |
Range percentage |  | 30.00% |  | 0.00%
Variable Interest Entity Notes [Member] | Variable Interest Entity Primary Beneficiary [Member] | Impact Of Financial Guarantee [Member] | Maximum [Member] | Quoted market prices of VIE assets adjusted for financial guarantees provided [Member] |  |  |  |
Fair Value Assets Measured On Recurring Basis Unobservable Input Reconciliation [Line Items] |  |  |  |
Range percentage |  | 65.00% |  | 63.00%
Variable Interest Entity Notes [Member] | Variable Interest Entity Primary Beneficiary [Member] | Impact Of Financial Guarantee [Member] | Weighted Average [Member] | Quoted market prices of VIE assets adjusted for financial guarantees provided [Member] |  |  |  |
Fair Value Assets Measured On Recurring Basis Unobservable Input Reconciliation [Line Items] |  |  |  |
Range percentage |  | 53.00% |  | 39.00%
[1] | Midpoint of cash flows are used for the weighted average.
[2] | Negative percentage represents financial guarantee policies in a receivable position.

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