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Allowance for Credit Losses - Narrative (Details) - USD ($) $ in Millions | Sep. 30, 2021 | Jun. 30, 2021 | Dec. 31, 2020 | Sep. 30, 2020 | Jun. 30, 2020 | Dec. 31, 2019
--- | --- | --- | --- | --- | --- | ---
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |  |
Allowance for loan and lease losses | $ 734 | $ 815 | $ 963 | $ 988 | $ 538 | $ 307
COVID-19 Deferrals |  |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |  |
Allowance for loan and lease losses | $ 1 |  | $ 1 |  |  |

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- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. + References No definition available. + Details
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Namespace Prefix: | us-gaap_
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Balance Type: | na
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- Definition Amount excluding accrued interest, of allowance for credit loss on financing receivable. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 326 -SubTopic 20 -Section 45 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=124255206&loc=SL82895884-210446 + Details
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Namespace Prefix: | us-gaap_
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Balance Type: | credit
Period Type: | instant

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- Details
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