Loans and Allowance for Credit Losses - Modifications Narrative (Details) $ in Millions	6 Months Ended	12 Months Ended
Jun. 30, 2021 USD ($) loan	Jun. 30, 2020 loan	Dec. 31, 2020 USD ($) loan
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of contracts modified in TDR	0	0
Cares Act and ASC 310-40 \| Payment Deferral
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of contracts modified in TDR	31		36
Troubled debt restructuring \| $	$ 77		$ 72
Troubled debt restructuring, percent of total loans	1.10%		0.90%

Financing Receivable, Troubled Debt Restructuring, Percent of Total Loans

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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.

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- Definition

Number of financing receivables that have been modified by troubled debt restructurings.

+ References

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- Definition

Amount of financing receivable modified as troubled debt restructuring.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 33
-URI http://asc.fasb.org/extlink&oid=121611835&loc=SL6953676-111524

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-Publisher FASB
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-Topic 310
-SubTopic 40
-Section 50
-Paragraph 4
-URI http://asc.fasb.org/extlink&oid=121585226&loc=d3e18845-111554

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