Investment Securities - Schedule of Scheduled Contractual Maturities of Investment Securities (Parenthetical) (Detail)	Jun. 30, 2013
Amortized Cost And Fair Value Debt Securities [Abstract]
Contractual maturities for investments with no stated maturities, in years	10 years

Contractual maturities for investments with no stated maturities.

No definition available.

Name:	cof_ContractualMaturitiesForInvestmentsWithNoStatedMaturities
Namespace Prefix:	cof_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	instant