Net Funded Status (Detail) - USD ($) $ in Millions	Dec. 31, 2015	Dec. 31, 2014
Defined Benefit Plan Disclosure [Line Items]
Net underfunded status	$ (54)	$ (52)
Underfunded Defined Benefit Pension Plans
Defined Benefit Plan Disclosure [Line Items]
Accrued benefit liability	$ (54)	$ (52)

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

No definition available.

+ Details

Name:	us-gaap_DefinedBenefitPlanDisclosureLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

The funded status is measured as the difference between the fair value of plan assets and the benefit obligation. Will normally be the same as the net Defined Benefit Plan, Amounts Recognized in Balance Sheet, Total.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=58740216&loc=d3e1928-114920

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=21915240&loc=d3e1703-114919

+ Details

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

- Definition

If aggregate disclosures are presented, the aggregate benefit obligation for plans with benefit obligations in excess of plan assets as of the measurement date of each statement of financial position presented.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 3
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=58740216&loc=d3e2417-114920

+ Details

Name:	us-gaap_DefinedBenefitPlanPlansWithBenefitObligationsInExcessOfPlanAssetsAggregateBenefitObligation
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Details

Name:	us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis=fitb_UnderfundedDefinedBenefitPensionPlansMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: