Troubled Debt Restructuring Additional Information (Detail) (USD $) In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Troubled Debt Restructuring
Line of credit and letter of credit commitments for modified troubled debt restructurings	$ 89	$ 86

Line of credit and letter of credit commitments to lend additional funds to debtors owing receivables whose terms have been modified in a troubled debt restructuring.

No definition available.

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