Defined Benefit Plans with Assets Exceeding Benefit Obligations (Detail) (USD $) In Millions, unless otherwise specified	Dec. 31, 2010
Schedule Of Pension Plans With Plan Assets Exceeding Benefit Obligations [Line Items]
Projected benefit obligation	$ 193
Fair value of plan assets	197
Accumulated benefit obligation	$ 193

Defined Benefit Plan, Plans with Plan Assets in Excess of Accumulated Benefit Obligations, Aggregate Projected Benefit Obligation

No definition available.

Name:	fitb_DefinedBenefitPlanPlansWithPlanAssetsInExcessOfAccumulatedBenefitObligationsAggregateProjectedBenefitObligation
Namespace Prefix:	fitb_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant