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Fair Value Measurements (Summary Of Quantitative Information About Level 3 Fair Value Measurements) (Details) - Discounted Cash Flow [Member] - Residential Mortgage [Member] $ in Millions | Sep. 30, 2023 USD ($) | Dec. 31, 2022 USD ($)
--- | --- | ---
Level 3 [Member] |  |
Fair Value Measurement Inputs and Valuation Techniques [Line Items] |  |
Assets, Fair Value Disclosure | $ 932 | $ 812
Recurring Fair Value Measurements [Member] | Minimum [Member] |  |
Fair Value Measurement Inputs and Valuation Techniques [Line Items] |  |
Weighted Average CPR | 0.055 | 0.061
Option-Adjusted Spread | 4.50% | 4.80%
Recurring Fair Value Measurements [Member] | Maximum [Member] |  |
Fair Value Measurement Inputs and Valuation Techniques [Line Items] |  |
Weighted Average CPR | 0.133 | 0.151
Option-Adjusted Spread | 8.20% | 8.20%
Recurring Fair Value Measurements [Member] | Weighted Average [Member] |  |
Fair Value Measurement Inputs and Valuation Techniques [Line Items] |  |
Weighted Average CPR | 0.077 | 0.074
Option-Adjusted Spread | 4.80% | 5.10%

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- Definition Fair value portion of probable future economic benefits obtained or controlled by an entity as a result of past transactions or events. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Name Accounting Standards Codification -Topic 820 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (a) -Publisher FASB -URI https://asc.fasb.org//1943274/2147482106/820-10-50-2 + Details
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