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Variable Interest Entities and Securitizations - Additional Information (Detail) - USD ($) $ in Millions | 12 Months Ended
--- | ---
Dec. 31, 2019 | Dec. 31, 2018
Variable Interest Entity [Line Items] |  |
Amortization method qualified affordable housing investments, amortization | $ 554 | $ 477
Affordable housing tax credits | 610 | 529
Amortization method qualified affordable housing investments | 4,400 | 4,200
Qualified affordable housing investments, commitment | 1,500 | 1,500
VIE, unconsolidated, carrying amount, assets | 5,127 | 4,802
VIE, consolidated, carrying amount, assets | 35,519 | 35,556
VIE, reporting entity involvement, maximum loss exposure | 5,413 | 5,145
Affordable housing entities |  |
Variable Interest Entity [Line Items] |  |
VIE, unconsolidated, carrying amount, assets | 4,559 | 4,238
Total assets of the unconsolidated VIE investment funds | 10,900 | 10,800
VIE, consolidated, carrying amount, assets | 236 | 243
VIE, reporting entity involvement, maximum loss exposure | 4,559 | 4,238
Entities that provide capital to low-income and rural communities |  |
Variable Interest Entity [Line Items] |  |
VIE, unconsolidated, carrying amount, assets | 0 | 0
VIE, consolidated, carrying amount, assets | 1,889 | 1,739
VIE, reporting entity involvement, maximum loss exposure | 0 | 0
Other |  |
Variable Interest Entity [Line Items] |  |
VIE, unconsolidated, carrying amount, assets | 502 | 353
VIE, consolidated, carrying amount, assets | 0 | 0
VIE, reporting entity involvement, maximum loss exposure | $ 502 | $ 353

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- Definition Variable Interest Entity, Nonconsolidated, Total Assets + References No definition available. + Details
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Namespace Prefix: | cof_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

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- Definition Amount of affordable housing tax credits and other tax benefits recognized. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 323 -SubTopic 740 -Section 50 -Paragraph 2 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=116633289&loc=SL49122993-202985 + Details
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Namespace Prefix: | us-gaap_
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Balance Type: | credit
Period Type: | duration

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- Definition Amount of investment in qualified affordable housing projects. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 323 -SubTopic 740 -Section 50 -Paragraph 2 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=116633289&loc=SL49122993-202985 + Details
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Period Type: | instant

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- Definition Amount of amortization expense of investment in qualified affordable housing projects. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 323 -SubTopic 740 -Section 50 -Paragraph 2 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=116633289&loc=SL49122993-202985 + Details
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- Definition Amount of commitment or contingent commitments to qualified affordable housing project investments. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 323 -SubTopic 740 -Section 50 -Paragraph 2 -Subparagraph (e) -URI http://asc.fasb.org/extlink&oid=116633289&loc=SL49122993-202985 + Details
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- Definition The carrying amount of the consolidated Variable Interest Entity's assets included in the reporting entity's statement of financial position. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 810 -SubTopic 10 -Section 50 -Paragraph 3 -Subparagraph (bb) -URI http://asc.fasb.org/extlink&oid=118582676&loc=d3e5710-111685 + Details
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- Definition The reporting entity's maximum amount of exposure to loss as a result of its involvement with the Variable Interest Entity (VIE). + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 810 -SubTopic 10 -Section 50 -Paragraph 6 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=118582676&loc=d3e5747-111685 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 810 -SubTopic 10 -Section 50 -Paragraph 4 -Subparagraph b -URI http://asc.fasb.org/extlink&oid=118582676&loc=d3e5728-111685 + Details
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- 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
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- Definition Carrying amount of the assets in the reporting entity's statement of financial position that relate to the reporting entity's variable interest in the Variable Interest Entity (VIE), where the reporting entity is not the VIE's primary beneficiary. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 810 -SubTopic 10 -Section 50 -Paragraph 4 -Subparagraph a -URI http://asc.fasb.org/extlink&oid=118582676&loc=d3e5728-111685 + Details
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- Details
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- Details
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