Fair Value Measurements (Rollforward For Assets And Liabilities Measured At Fair Value On A Recurring Basis With Level 3 Significant Unobservable Inputs) (Details) - Residential Mortgage Servicing Rights [Member] - USD ($) $ in Millions |
12 Months Ended | ||||
|---|---|---|---|---|---|
Dec. 31, 2020 |
Dec. 31, 2019 |
Dec. 31, 2018 |
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| Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward] | |||||
| Opening Balance | $ 345 | $ 418 | $ 336 | ||
| Gain (Loss) Included in Earnings | [1] | (157) | (115) | (29) | |
| Purchases | $ 108 | 42 | 111 | ||
| Closing Balance | $ 345 | $ 418 | |||
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