Regulatory and Capital Adequacy - Additional Information (Details) - USD ($) $ in Millions	12 Months Ended		36 Months Ended
	Dec. 31, 2023	Dec. 31, 2021	Dec. 31, 2025
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Regulatory capital adjustments, net of tax, CECL transition		$ 2,400
Regulatory capital adjustments, net of tax, CECL transition, phased in amount per year	$ 600
Common equity tier one capital ratio, CECL transition	12.90%
Common equity tier one capital ratio, excluding CECL transition adjustment	12.60%
Forecast
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Regulatory capital adjustments, net of tax, CECL transition, phased in amount			$ 1,200
Capital One Bank (USA), N.A.
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Funds available for dividend payments	$ 5,200