Regulatory and Capital Adequacy Regulatory and Capital Adequacy - Additional Information (Details) $ in Millions	Dec. 31, 2015 USD ($)
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
SLR Minimum Requirement	3.00%
Capital One Bank (USA), N.A.
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Funds available for dividend payments to parent	$ 2,900
Capital One, N.A.
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Funds available for dividend payments to parent	$ 359