Commitments (Visa Funding and Bancorp Cash Payments) (Parenthetical) (Detail) - USD ($) $ in Millions	1 Months Ended	3 Months Ended
Jul. 31, 2018	Sep. 30, 2014	Sep. 30, 2012	Mar. 31, 2012	Jun. 30, 2011	Dec. 31, 2010	Jun. 30, 2010
Bancorp Cash Payment
Loss Contingencies [Line Items]
Reduction of liability in cash to the swap counterparty	$ 26	$ 18	$ 6	$ 75	$ 19	$ 35	$ 20

The increase (decrease) during the period in the carrying value of derivative instruments reported as liabilities that are due to be disposed of within one year (or the normal operating cycle, if longer).

No definition available.

Name:	us-gaap_IncreaseDecreaseInDerivativeLiabilities
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration