Mortgage Loans on Real Estate, Face Amount of Mortgages, Sold to Third Party

No definition available.

Name:	cof_MortgageLoansonRealEstateFaceAmountofMortgagesSoldtoThirdParty
Namespace Prefix:	cof_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Original principal balance of mortgage loans originated and sold to non affiliates by subsidiaries between two thousand five and two thousand eight percent.

+ References

No definition available.

+ Details

Name:	cof_MortgageLoansonRealEstateFaceAmountofMortgagesSoldtoThirdPartyPercentCoveredbyBondInsurance
Namespace Prefix:	cof_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Mortgage Loans on Real Estate, Face Amount of Mortgages, Sold to Third Party, With Repurchase Requests

+ References

No definition available.

+ Details

Name:	cof_MortgageLoansonRealEstateFaceAmountofMortgagesSoldtoThirdPartyWithRepurchaseRequests
Namespace Prefix:	cof_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Mortgage Loans on Real Estate, Face Amount of Mortgages, Sold to Third Party, Without Repurchase Requests

+ References

No definition available.

+ Details

Name:	cof_MortgageLoansonRealEstateFaceAmountofMortgagesSoldtoThirdPartyWithoutRepurchaseRequests
Namespace Prefix:	cof_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Mortgage Loans on Real Estate, Sold to Third Parties, Losses Realized by Third Party

+ References

No definition available.

+ Details

Name:	cof_MortgageLoansonRealEstateSoldtoThirdPartiesLossesRealizedbyThirdParty
Namespace Prefix:	cof_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Mortgage Loans on Real Estate, Sold to Third Party [Abstract]

+ References

No definition available.

+ Details

Name:	cof_MortgageLoansonRealEstateSoldtoThirdPartyAbstract
Namespace Prefix:	cof_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Original principal balance of mortgage loans under current holders or underlying credit performance.

+ References

No definition available.

+ Details

Name:	cof_MortgageLoansonRealEstateSoldtoThirdPartyUnpaidPrincipalBalanceDelinquent90DaysorGreater
Namespace Prefix:	cof_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Mortgage Loans on Real Estate, Unpaid Principal Balances, Sold to Third Party

+ References

No definition available.

+ Details

Name:	cof_MortgageLoansonRealEstateUnpaidPrincipalBalancesSoldtoThirdParty
Namespace Prefix:	cof_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

The number of subsidiaries acquired that originated and sold residential mortgage loans.

+ References

No definition available.

+ Details

Name:	cof_NumberofAcquiredSubsidiariesthatOriginatedMortgagesLoansandSoldtoThirdParty
Namespace Prefix:	cof_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

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

- Definition

The difference between the maximum amount of estimated loss and the amount recorded as of the balance sheet date.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 450

-SubTopic 20

-Section 05

-Paragraph 5

-URI http://asc.fasb.org/extlink&oid=6395354&loc=d3e12631-108344

+ Details

Name:	us-gaap_LossContingencyRangeOfPossibleLossPortionNotAccrued
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Details

Name:	dei_LegalEntityAxis=us-gaap_SubsidiariesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	cof_MortgageLoanOriginationPeriodAxis=cof_MortgageLoansOriginatedbetween2005and2008Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	cof_MortgageLoanOriginationPeriodAxis=cof_MortgageLoansOriginated2008Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	cof_MortgageLoanOriginationPeriodAxis=cof_MortgageLoansOriginated2007Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	cof_MortgageLoanOriginationPeriodAxis=cof_MortgageLoansOriginated2006Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	cof_MortgageLoanOriginationPeriodAxis=cof_MortgageLoansOriginated2005Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_CounterpartyNameAxis=cof_GovernmentSponsoredEnterprisesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_CounterpartyNameAxis=cof_InsuredSecuritizationsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_CounterpartyNameAxis=cof_UninsuredSecuritizationsAndOtherWholeLoansSalesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_CounterpartyNameAxis=cof_UninsuredSecuritizationsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_CounterpartyNameAxis=cof_PrivateInvestorsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_CounterpartyNameAxis=cof_VariousKnownandUnknownInvestorsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LossContingenciesByNatureOfContingencyAxis=cof_RepresentationandWarrantyLiabilityMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Commitments, Contingencies, Guarantees, and Others - Schedule of Unpaid Principal Balance of Mortgage Loans Originated and Sold to Third Parties Based on Category of Purchaser (Details) $ in Billions	49 Months Ended
	Feb. 28, 2009 Subsidiary	Sep. 30, 2015 USD ($)	Dec. 31, 2014 USD ($)
Loss Contingencies [Line Items]
Number of subsidiaries acquired that originated residential mortgage loans \| Subsidiary	3
Mortgage Loans on Real Estate, Sold to Third Party [Abstract]
Losses realized by third party		$ 22.0
Subsidiaries
Mortgage Loans on Real Estate, Sold to Third Party [Abstract]
Estimated Unpaid Principal Balance		20.0	$ 23.0
Unpaid principal balance, delinquent 90 days or greater		4.0
Subsidiaries \| 2005 to 2008 Year
Mortgage Loans on Real Estate, Sold to Third Party [Abstract]
Original Principal Balance		111.0
Subsidiaries \| 2008
Mortgage Loans on Real Estate, Sold to Third Party [Abstract]
Original Principal Balance		4.0
Subsidiaries \| 2007
Mortgage Loans on Real Estate, Sold to Third Party [Abstract]
Original Principal Balance		21.0
Subsidiaries \| 2006
Mortgage Loans on Real Estate, Sold to Third Party [Abstract]
Original Principal Balance		41.0
Subsidiaries \| 2005
Mortgage Loans on Real Estate, Sold to Third Party [Abstract]
Original Principal Balance		45.0
Subsidiaries \| Government-sponsored enterprises (“GSEs”)
Mortgage Loans on Real Estate, Sold to Third Party [Abstract]
Estimated Unpaid Principal Balance		2.0	3.0
Subsidiaries \| Government-sponsored enterprises (“GSEs”) \| 2005 to 2008 Year
Mortgage Loans on Real Estate, Sold to Third Party [Abstract]
Original Principal Balance		11.0
Subsidiaries \| Government-sponsored enterprises (“GSEs”) \| 2008
Mortgage Loans on Real Estate, Sold to Third Party [Abstract]
Original Principal Balance		1.0
Subsidiaries \| Government-sponsored enterprises (“GSEs”) \| 2007
Mortgage Loans on Real Estate, Sold to Third Party [Abstract]
Original Principal Balance		4.0
Subsidiaries \| Government-sponsored enterprises (“GSEs”) \| 2006
Mortgage Loans on Real Estate, Sold to Third Party [Abstract]
Original Principal Balance		3.0
Subsidiaries \| Government-sponsored enterprises (“GSEs”) \| 2005
Mortgage Loans on Real Estate, Sold to Third Party [Abstract]
Original Principal Balance		3.0
Subsidiaries \| Insured Securitizations
Mortgage Loans on Real Estate, Sold to Third Party [Abstract]
Estimated Unpaid Principal Balance		4.0	4.0
Subsidiaries \| Insured Securitizations \| 2005 to 2008 Year
Mortgage Loans on Real Estate, Sold to Third Party [Abstract]
Original Principal Balance		$ 20.0
Percent covered by bond insurance		48.00%
Original principal balance, sold to third party with repurchase requests		$ 16.0
Original principal balance, sold to third party without repurchase requests		4.0
Subsidiaries \| Insured Securitizations \| 2008
Mortgage Loans on Real Estate, Sold to Third Party [Abstract]
Original Principal Balance		0.0
Subsidiaries \| Insured Securitizations \| 2007
Mortgage Loans on Real Estate, Sold to Third Party [Abstract]
Original Principal Balance		2.0
Subsidiaries \| Insured Securitizations \| 2006
Mortgage Loans on Real Estate, Sold to Third Party [Abstract]
Original Principal Balance		8.0
Subsidiaries \| Insured Securitizations \| 2005
Mortgage Loans on Real Estate, Sold to Third Party [Abstract]
Original Principal Balance		10.0
Subsidiaries \| Uninsured Securitizations and Other
Mortgage Loans on Real Estate, Sold to Third Party [Abstract]
Estimated Unpaid Principal Balance		14.0	16.0
Subsidiaries \| Uninsured Securitizations and Other \| 2005 to 2008 Year
Mortgage Loans on Real Estate, Sold to Third Party [Abstract]
Original Principal Balance		80.0
Subsidiaries \| Uninsured Securitizations and Other \| 2008
Mortgage Loans on Real Estate, Sold to Third Party [Abstract]
Original Principal Balance		3.0
Subsidiaries \| Uninsured Securitizations and Other \| 2007
Mortgage Loans on Real Estate, Sold to Third Party [Abstract]
Original Principal Balance		15.0
Subsidiaries \| Uninsured Securitizations and Other \| 2006
Mortgage Loans on Real Estate, Sold to Third Party [Abstract]
Original Principal Balance		30.0
Subsidiaries \| Uninsured Securitizations and Other \| 2005
Mortgage Loans on Real Estate, Sold to Third Party [Abstract]
Original Principal Balance		32.0
Subsidiaries \| Uninsured Securitizations \| 2005 to 2008 Year
Mortgage Loans on Real Estate, Sold to Third Party [Abstract]
Original Principal Balance		48.0
Subsidiaries \| Private Investors \| 2005 to 2008 Year
Mortgage Loans on Real Estate, Sold to Third Party [Abstract]
Original Principal Balance		22.0
Subsidiaries \| Various Known and Unknown Investors \| 2005 to 2008 Year
Mortgage Loans on Real Estate, Sold to Third Party [Abstract]
Original Principal Balance		10.0
Representation and Warranty Liability [Member] \| Subsidiaries
Loss Contingencies [Line Items]
Loss Contingency, Range of Possible Loss, Portion Not Accrued		$ 1.6	$ 2.1