Summary of Significant Accounting and Reporting Policies - Pension Plans (Details)	12 Months Ended
Dec. 31, 2020
Accounting Policies [Abstract]
Net gain (loss) in excess of projected benefit obligation, percentage	10.00%

Defined Benefit Plan, Net Gain (Loss) In Excess Of Projected Benefit Obligation, Percentage

No definition available.

Name:	fitb_DefinedBenefitPlanNetGainLossInExcessOfProjectedBenefitObligationPercentage
Namespace Prefix:	fitb_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration