XML 42 R100.htm IDEA: XBRL DOCUMENT
v3.19.3.a.u2

Regulatory and Capital Adequacy - Additional Information (Details) - USD ($) $ in Billions | Dec. 31, 2019 | Dec. 31, 2018
--- | --- | ---
Cash Reserves, Federal Reserve Bank |  |
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items] |  |
Cash Reserve Deposit Required and Made | $ 1.7 | $ 1.9
Capital One Bank (USA), N.A. |  |
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items] |  |
Statutory Accounting Practices, Statutory Amount Available for Dividend Payments | 3.3 |
Capital One, N.A. |  |
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items] |  |
Statutory Accounting Practices, Statutory Amount Available for Dividend Payments | $ 4.7 |

X
- Definition Cash deposited in a special reserve account for the exclusive benefit of customers pursuant to SEC Regulations. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 210 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=116631393&loc=SL116631396-227033 + Details
Name: | us-gaap_CashReserveDepositRequiredAndMade
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

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_ComplianceWithRegulatoryCapitalRequirementsUnderBankingRegulationsLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Amount of dividends available for payment after computation of statutory restrictions on capital surplus. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 235 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.4-08.(e)) -URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e23780-122690 + Details
Name: | us-gaap_StatutoryAccountingPracticesStatutoryAmountAvailableForDividendPayments
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Details
Name: | us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsAxis=cof_CashReservesFederalReserveBankMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | dei_LegalEntityAxis=cof_CapitalOneBankUSAN.A.Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | dei_LegalEntityAxis=cof_CapitalOneN.A.Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |