Cover Page - USD ($) $ in Billions	12 Months Ended
	Dec. 31, 2021	Jan. 31, 2022	Jun. 30, 2021
Entity Information [Line Items]
Document Type	10-K
Document Annual Report	true
Document Period End Date	Dec. 31, 2021
Current Fiscal Year End Date	--12-31
Document Transition Report	false
Entity File Number	001-13300
Entity Registrant Name	CAPITAL ONE FINANCIAL CORP
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	54-1719854
Entity Address, Address Line One	1680 Capital One Drive,
Entity Address, City or Town	McLean,
Entity Address, State or Province	VA
Entity Address, Postal Zip Code	22102
City Area Code	703
Local Phone Number	720-1000
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
ICFR Auditor Attestation Flag	true
Entity Shell Company	false
Entity Public Float			$ 68.4
Entity Common Stock, Shares Outstanding		413,661,098
Documents Incorporated by Reference	Portions of the Proxy Statement for the annual meeting of stockholders to be held on May 5, 2022, are incorporated by reference into Part III.
Amendment Flag	false
Document Fiscal Year Focus	2021
Document Fiscal Period Focus	FY
Entity Central Index Key	0000927628
Common Stock (par value $.01 per share)
Entity Information [Line Items]
Title of 12(b) Security	Common Stock (par value $.01 per share)
Trading Symbol	COF
Security Exchange Name	NYSE
Depositary Shares, Each Representing a 1/40th Interest in a Share of Fixed Rate Non-Cumulative Perpetual Preferred Stock, Series I
Entity Information [Line Items]
Title of 12(b) Security	Depositary Shares, Each Representing a 1/40th Interest in a Share of Fixed Rate Non-Cumulative Perpetual Preferred Stock, Series I
Trading Symbol	COF PRI
Security Exchange Name	NYSE
Depositary Shares, Each Representing a 1/40th Interest in a Share of Fixed Rate Non-Cumulative Perpetual Preferred Stock, Series J
Entity Information [Line Items]
Title of 12(b) Security	Depositary Shares, Each Representing a 1/40th Interest in a Share of Fixed Rate Non-Cumulative Perpetual Preferred Stock, Series J
Trading Symbol	COF PRJ
Security Exchange Name	NYSE
Depositary Shares, Each Representing a 1/40th Interest in a Share of Fixed Rate Non-Cumulative Perpetual Preferred Stock, Series K
Entity Information [Line Items]
Title of 12(b) Security	Depositary Shares, Each Representing a 1/40th Interest in a Share of Fixed Rate Non-Cumulative Perpetual Preferred Stock, Series K
Trading Symbol	COF PRK
Security Exchange Name	NYSE
Depositary Shares, Each Representing a 1/40th Interest in a Share of Fixed Rate Non-Cumulative Perpetual Preferred Stock, Series L
Entity Information [Line Items]
Title of 12(b) Security	Depositary Shares, Each Representing a 1/40th Interest in a Share of Fixed Rate Non-Cumulative Perpetual Preferred Stock, Series L
Trading Symbol	COF PRL
Security Exchange Name	NYSE
Depositary Shares, Each Representing a 1/40th Interest in a Share of Fixed Rate Non-Cumulative Perpetual Preferred Stock, Series N
Entity Information [Line Items]
Title of 12(b) Security	Depositary Shares, Each Representing a 1/40th Interest in a Share of Fixed Rate Non-Cumulative Perpetual Preferred Stock, Series N
Trading Symbol	COF PRN
Security Exchange Name	NYSE
0.800% Senior Notes Due 2024
Entity Information [Line Items]
Title of 12(b) Security	0.800% Senior Notes Due 2024
Trading Symbol	COF24
Security Exchange Name	NYSE
1.650% Senior Notes Due 2029
Entity Information [Line Items]
Title of 12(b) Security	1.650% Senior Notes Due 2029
Trading Symbol	COF29
Security Exchange Name	NYSE