Regulatory and Capital Adequacy - Additional Information (Details)		12 Months Ended	36 Months Ended
	Jan. 01, 2022 USD ($)	Dec. 31, 2021 USD ($)	Dec. 31, 2025 USD ($)	Dec. 31, 2022 USD ($)
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Common equity Tier 1 capital		$ 43,501,000,000		$ 44,731,000,000
Common equity Tier 1 capital, capital ratio		0.131		0.125
Regulatory Capital Adjustments, Net of Tax, CECL Transition		$ 2,400,000,000
Common Equity Tier One Capital Ratio, CECL Transition				12.50%
Common Equity Tier One Capital Ratio, Excluding CECL Transition Adjustment				12.00%
Regulatory Capital Adjustments, Net of Tax, CECL Transition, Phased in Amount	$ 599,000,000
Forecast
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Regulatory Capital Adjustments, Net of Tax, CECL Transition, Phased in Amount			$ 1,800,000,000
Capital One Bank (USA), N.A.
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Funds available for dividend payments				$ 3,200,000,000
Capital One, N.A.
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Common equity Tier 1 capital		$ 26,699,000,000		$ 46,630,000,000
Common equity Tier 1 capital, capital ratio		0.111		0.131