Allowance For Credit Losses (Narrative) (Details) - USD ($) $ in Millions |
3 Months Ended | 12 Months Ended | ||
|---|---|---|---|---|
Mar. 31, 2020 |
Dec. 31, 2020 |
Dec. 31, 2019 |
Dec. 31, 2018 |
|
| Accounts, Notes, Loans and Financing Receivable [Line Items] | ||||
| Payroll Protection Program loans | $ 3,600 | |||
| Provision for credit losses (1) | 878 | |||
| Provision for credit losses (1) | 2,293 | $ 914 | $ 891 | |
| CECL [Member] | ||||
| Accounts, Notes, Loans and Financing Receivable [Line Items] | ||||
| Provision for credit losses (1) | $ 501 | |||
| Commercial Portfolio Segment [Member] | ||||
| Accounts, Notes, Loans and Financing Receivable [Line Items] | ||||
| Financing Receivable, Nonaccrual, No Allowance | $ 112 | |||
| Minimum [Member] | ||||
| Accounts, Notes, Loans and Financing Receivable [Line Items] | ||||
| Financing period for consumer loans, in years | 15 years | |||
| Maximum [Member] | ||||
| Accounts, Notes, Loans and Financing Receivable [Line Items] | ||||
| Financing period for consumer loans, in years | 30 years |