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Employee Benefit Plans - Defined Contribution Plan Narrative (Details) $ in Millions | 12 Months Ended
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Dec. 31, 2022 USD ($) age | Dec. 31, 2021 USD ($) | Dec. 31, 2020 USD ($)
Defined Contribution Plan Disclosure [Line Items] |  |  |
Defined contribution plan, cost | $ | $ 444 | $ 378 | $ 350
Associate Savings Plan |  |  |
Defined Contribution Plan Disclosure [Line Items] |  |  |
Defined contribution plan, age eligible to participate | age | 18 |  |

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- Definition Defined Contribution Plan, Age Eligible to Participate + References No definition available. + Details
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Namespace Prefix: | cof_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | instant

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- Definition Amount of cost for defined contribution plan. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 70 -Section 50 -Paragraph 1 -URI https://asc.fasb.org/extlink&oid=49170846&loc=d3e28014-114942 + Details
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Balance Type: | debit
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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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Data Type: | xbrli:stringItemType
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- Details
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Namespace Prefix: |
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Balance Type: |
Period Type: |