Name:	cof_AvailableforsaleSecuritiesDebtMaturitiesRollingafterYearTenandWithoutSingleMaturityDateAmortizedCostBasis
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Available-for-sale Securities, Debt Maturities, and Without Single Maturity Date, Rolling after Year Ten, Fair Value

No definition available.

Name:	cof_AvailableforsaleSecuritiesDebtMaturitiesandWithoutSingleMaturityDateRollingafterYearTenFairValue
Namespace Prefix:	cof_
Data Type:	xbrli:monetaryItemType
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Period Type:	instant

Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 25
-Paragraph 1
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=51813488&loc=d3e22054-111558

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 5
-Subparagraph (aa)
-URI http://asc.fasb.org/extlink&oid=27724398&loc=d3e27232-111563

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=49167202&loc=d3e26610-111562

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This item represents the cost of debt and equity securities, which are categorized neither as held-to-maturity nor trading, net of adjustments including accretion, amortization, collection of cash, previous other-than-temporary impairments recognized in earnings (less any cumulative-effect adjustments recognized, as defined), and fair value hedge accounting adjustments, if any.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.2)
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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Period Type:	instant

- References

No definition available.

Name:	us-gaap_AvailableForSaleSecuritiesDebtMaturitiesFairValueRollingMaturityAbstract
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Period Type:	duration

Amount after adjustments of available-for-sale debt securities at cost, maturing in the next rolling twelve months following the latest balance sheet. Adjustments include, but are not limited to, accretion, amortization, collection of cash, previous other-than-temporary impairments (OTTI) recognized in earnings less cumulative-effect adjustments and fair value hedge accounting adjustments. For interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

No definition available.

Name:	us-gaap_AvailableForSaleSecuritiesDebtMaturitiesNextRollingTwelveMonthsAmortizedCostBasis
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
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Fair value of available-for-sale debt securities maturing in the next rolling twelve months following the latest balance sheet. For interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

No definition available.

Name:	us-gaap_AvailableForSaleSecuritiesDebtMaturitiesNextRollingTwelveMonthsFairValue
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
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Period Type:	instant

Amount after adjustments of available-for-sale debt securities at cost, maturing in the sixth through tenth rolling twelve months following the latest balance sheet. Adjustments include, but are not limited to, accretion, amortization, collection of cash, previous other-than-temporary impairments (OTTI) recognized in earnings less cumulative-effect adjustments, and fair value hedge accounting adjustments. For interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

No definition available.

Name:	us-gaap_AvailableForSaleSecuritiesDebtMaturitiesRollingYearSixThroughTenAmortizedCostBasis
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
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Period Type:	instant

Fair value of available-for-sale debt securities maturing in the sixth through tenth rolling twelve months following the latest balance sheet. For interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

No definition available.

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

Amount after adjustments of available-for-sale debt securities at cost, maturing in the second through fifth rolling twelve months following the latest balance sheet. Adjustments include, but are not limited to, accretion, amortization, collection of cash, previous other-than-temporary impairments (OTTI) recognized in earnings less cumulative-effect adjustments, and fair value hedge accounting adjustments. For interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

No definition available.

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

Fair value of available-for-sale debt securities maturing in the second through fifth rolling twelve months following the latest balance sheet. For interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

No definition available.

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

- References

No definition available.