Credit Quality Additional Information (Detail) - USD ($) $ in Millions	Sep. 30, 2015	Sep. 30, 2014
Troubled Debt Restructuring
Line of credit commitments for modified troubled debt restructurings	$ 50	$ 63
Letter of credit commitments for modified troubled debt restructurings	32	$ 26
Mortgage Loans In Process Of Foreclosure Amount	$ 310

Recorded investment of consumer mortgage loan receivables secured by residential real estate properties for which formal foreclosure proceedings are in process.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 310

-SubTopic 10

-Section 50

-Paragraph 35

-URI http://asc.fasb.org/extlink&oid=49124121&loc=SL49126937-111524

Name:	us-gaap_MortgageLoansInProcessOfForeclosureAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant