XML 79 R54.htm IDEA: XBRL DOCUMENT
v3.22.4

Summary of Significant Accounting Policies - Arrangements (Details) - USD ($) $ in Billions | 12 Months Ended
--- | ---
Dec. 31, 2021 | Dec. 31, 2020
Collaborative Arrangement |  |
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items] |  |
Reduction of interest income | $ 1.0 | $ 1.1

X
- Definition Collaborative Arrangement, Revenue As Reduction To Interest Income + References No definition available. + Details
Name: | cof_CollaborativeArrangementRevenueAsReductionToInterestIncome
Namespace Prefix: | cof_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- 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
Name: | us-gaap_CollaborativeArrangementsAndNoncollaborativeArrangementTransactionsLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Details
Name: | us-gaap_TypeOfArrangementAxis=us-gaap_CollaborativeArrangementMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |