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Fair Value Measurements (Summary Of Quantitative Information About Level 3 Fair Value Measurements) (Details) $ in Millions	9 Months Ended	12 Months Ended
	Sep. 30, 2025 USD ($)	Dec. 31, 2024 USD ($)
Level 3 [Member] | Residential Mortgage
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Assets, Fair Value Disclosure	$ 976	$ 1,007
Level 3 [Member] | Commercial Real Estate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Assets, Fair Value Disclosure	$ 91	$ 97
Recurring Fair Value Measurements | Minimum [Member] | Discounted Cash Flow [Member] | Residential Mortgage
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Weighted Average CPR	0.040	0.046
Option-Adjusted Spread	4.70%	4.80%
Recurring Fair Value Measurements | Minimum [Member] | Discounted Cash Flow [Member] | Commercial Real Estate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Weighted Average CPR	0.066	0.054
Measurement Input, Discount Rate	8.00%	7.00%
Recurring Fair Value Measurements | Maximum [Member] | Discounted Cash Flow [Member] | Residential Mortgage
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Weighted Average CPR	0.187	0.231
Option-Adjusted Spread	8.00%	7.70%
Recurring Fair Value Measurements | Maximum [Member] | Discounted Cash Flow [Member] | Commercial Real Estate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Weighted Average CPR	0.077	0.106
Measurement Input, Discount Rate	10.00%	8.00%
Recurring Fair Value Measurements | Weighted Average [Member] | Discounted Cash Flow [Member] | Residential Mortgage
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Weighted Average CPR	0.077	0.080
Option-Adjusted Spread	5.00%	5.10%
Recurring Fair Value Measurements | Weighted Average [Member] | Discounted Cash Flow [Member] | Commercial Real Estate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Weighted Average CPR	0.076	0.077
Measurement Input, Discount Rate	8.20%	7.10%

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