Fair Value Measurements (Summary Of Quantitative Information About Level 3 Fair Value Measurements) (Details) - Mortgage Servicing Rights [Member] - Discounted Cash Flow [Member]
$ in Millions

12 Months Ended

Dec. 31, 2019

USD ($)

Dec. 31, 2018

USD ($)

Dec. 31, 2017

USD ($)

Level 3 [Member]

Fair Value Measurement Inputs and Valuation Techniques [Line Items]

Assets, Fair Value Disclosure

$ 345

$ 418

$ 336

Recurring Fair Value Measurements [Member] | Minimum [Member]

Fair Value Measurement Inputs and Valuation Techniques [Line Items]

Weighted Average CPR

^[1]

0.074

0.044

0.079

Option-Adjusted Spread

^[1]

5.20%

5.70%

8.10%

Recurring Fair Value Measurements [Member] | Maximum [Member]

Fair Value Measurement Inputs and Valuation Techniques [Line Items]

Weighted Average CPR

^[1]

0.261

0.426

0.281

Option-Adjusted Spread

^[1]

10.20%

15.00%

15.00%

Recurring Fair Value Measurements [Member] | Weighted Average [Member]

Fair Value Measurement Inputs and Valuation Techniques [Line Items]

Weighted Average CPR

^[1]

0.120

0.090

0.099

Option-Adjusted Spread

^[1]

6.18%

7.60%

8.60%

[1]	See Note 7 for additional disclosures related to assumptions used in the fair value calculation for residential mortgage servicing rights.