Summary of Significant Accounting Policies (Policies)	6 Months Ended
Summary of Significant Accounting Policies (Policies)	Jun. 30, 2016
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation and Use of Estimates The accompanying unaudited consolidated financial statements have been prepared in accordance with generally accepted accounting principles in the U.S. (“U.S. GAAP”).
Use of Estimates	The preparation of financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the amounts reported in the consolidated financial statements and in the related disclosures. These estimates are based on information available as of the date of the consolidated financial statements. While management makes its best judgment, actual amounts or results could differ from these estimates. In the opinion of management, all normal, recurring adjustments have been included for a fair statement of this interim financial information. Certain prior period amounts have been reclassified to conform to the current period presentation.
Principles of Consolidation	Principles of Consolidation The unaudited consolidated financial statements include the accounts of Capital One Financial Corporation and all other entities in which we have a controlling financial interest. We determine whether we have a controlling financial interest in an entity by first evaluating whether the entity is a voting interest entity or a variable interest entity (“VIE”). All significant intercompany account balances and transactions have been eliminated.
New Accounting Standards Adopted	New Accounting Standards Adopted Consolidation: Amendments to the Consolidation Analysis In February 2015, the Financial Accounting Standards Board (“FASB”) issued revised guidance for evaluating whether organizations should consolidate certain legal entities such as limited partnerships, limited liability corporations and securitization structures. The guidance also removed the indefinite deferral of specialized guidance for certain investment funds. We adopted the guidance effective in the first quarter of 2016 on a modified retrospective basis. Our adoption of this guidance did not have an impact on our financial condition, results of operations or liquidity. See “Note 6—Variable Interest Entities and Securitizations” for information regarding our involvement with VIEs. Recently Issued but Not Yet Adopted Accounting Standards Measurement of Credit Losses on Financial Instruments In June 2016, the FASB issued revised guidance for impairments on financial instruments. The guidance requires an impairment model (known as the current expected credit loss [“CECL”] model) that is based on expected rather than incurred losses, with an anticipated result of more timely loss recognition. The CECL model applies to loans held for investment, securities held to maturity, lease receivables, financial guarantee contracts and certain unconditional loan commitments. The CECL model will replace our current accounting for purchased credit-impaired (“PCI”) and impaired loans. The guidance also amends the available for sale (“AFS”) debt securities other-than-temporary impairments (“OTTI”) model. Credit losses (and subsequent recoveries) on AFS debt securities will be recorded through an allowance approach, rather than the current U.S. GAAP practice of permanent write-downs for credit losses and accreting positive changes through interest income over time. This guidance will be effective for us on January 1, 2020, with early adoption permitted no earlier than January 1, 2019. We are currently assessing the potential impact on our consolidated financial statements. Improvements to Employee Share-Based Accounting In March 2016, the FASB issued revised guidance for accounting for employee share-based payments, including the accounting for income taxes, forfeitures and statutory tax withholding requirements, as well as classification in the statement of cash flows. The guidance is effective beginning on January 1, 2017, with early adoption permitted. We do not believe the impact of this guidance will be material to our consolidated financial statements. Leases In February 2016, the FASB issued revised guidance for leases. The guidance requires lessees to recognize right of use assets and lease liabilities on the balance sheet and disclose key information about leasing arrangements for all leases, with certain practical expedients. This will be effective for us on January 1, 2019, with early adoption permitted. We are currently assessing the potential impact on our consolidated financial statements. Revenue from Contracts with Customers In May 2014, the FASB issued revised guidance for the recognition, measurement and disclosure of revenue from contracts with customers. The guidance is applicable to all entities and, once effective, will replace significant portions of existing industry and transaction-specific revenue recognition rules with a more principles-based recognition model. Most revenue associated with financial instruments, including interest and loan origination fees, is outside the scope of the guidance. Gains and losses on investment securities, derivatives and sales of financial instruments are similarly excluded from the scope. Subsequent to issuance of the revenue recognition guidance, the FASB has issued several updates, most notably that (i) deferred by one year the effective date for revenue recognition guidance to January 1, 2018, with early adoption permitted effective January 1, 2017; (ii) clarified its guidance for performing the principle-versus-agent analysis; and (iii) clarified guidance for identifying performance obligations allowing entities to ignore immaterial promised goods and services in the context of a contract with a customer. Entities can elect to adopt the guidance either on a full or modified retrospective basis. Full retrospective adoption will require a cumulative effect adjustment to retained earnings as of the beginning of the earliest comparative period presented. Modified retrospective adoption will require a cumulative effect adjustment to retained earnings as of the beginning of the reporting period in which the entity first applies the new guidance. We do not plan to early adopt the guidance. We are currently assessing the potential impact of this new guidance on our consolidated financial statements and which transition method we plan to elect.
Offsetting of Financial Assets and Liabilities	Offsetting of Financial Assets and Liabilities Derivative contracts and repurchase agreements that we execute bilaterally in the OTC market are governed by enforceable master netting arrangements where we generally have the right to offset exposure with the same counterparty. Either counterparty can generally request to net settle all contracts through a single payment upon default on, or termination of, any one contract. We elect to offset the derivative assets and liabilities under netting arrangements for balance sheet presentation where a right of setoff exists. Derivative contracts that are cleared with central clearinghouses through our Future Commission Merchants (“FCMs”) are not subject to offsetting due to the uncertainty existing around an end-user’s ability to setoff these derivative contracts.