Regulatory and Capital Adequacy Regulatory and Capital Adequacy - Additional Information (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2014
Capital One Bank (USA), N.A.
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Funds available for dividend payments to parent	$ 1,600
Capital One, N.A.
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Funds available for dividend payments to parent	$ 281

Amount of dividends available for payment after computation of statutory restrictions on capital surplus.

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

-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

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 08

-Paragraph e

-Article 4

Name:	us-gaap_StatutoryAccountingPracticesStatutoryAmountAvailableForDividendPayments
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant