Credit Quality Additional Information (Detail) (USD $) In Millions, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014
Troubled Debt Restructuring
Line of credit commitments for modified troubled debt restructurings	$ 56fitb_LineOfCreditCommitments	$ 63fitb_LineOfCreditCommitments
Letter of credit commitments for modified troubled debt restructurings	23fitb_LetterOfCreditCommitments	26fitb_LetterOfCreditCommitments
Mortgage Loans In Process Of Foreclosure Amount	$ 355

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

No definition available.

Name:	fitb_MortgageLoansInProcessOfForeclosureAmount
Namespace Prefix:	fitb_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant