Credit Quality and the Allowance for Loan and Lease Losses - Summary of Financial Impacts of Loans That Were Modified for Borrowers Experiencing Financial Difficulty (Details)	3 Months Ended	6 Months Ended
Jun. 30, 2025	Jun. 30, 2024	Jun. 30, 2025	Jun. 30, 2024
Commercial \| Commercial and industrial loans
Financing Receivable, Modifications
Weighted-average length of term extensions	20 months	10 months	16 months	9 months
Weighted-average length of payment delay	9 months	6 months	9 months	5 months
Commercial \| Commercial mortgage owner-occupied loans
Financing Receivable, Modifications
Weighted-average length of term extensions	6 months	12 months	7 months	9 months
Weighted-average length of payment delay	6 months	6 months	10 months	6 months
Commercial \| Commercial mortgage nonowner-occupied loans
Financing Receivable, Modifications
Weighted-average length of term extensions			6 months	6 months
Commercial \| Commercial construction loans
Financing Receivable, Modifications
Weighted-average length of term extensions	12 months	6 months	12 months	6 months
Weighted-average length of payment delay			7 months
Residential Mortgage
Financing Receivable, Modifications
Weighted-average length of term extensions	8 years 7 months 6 days	9 years 1 month 6 days	9 years 2 months 12 days	10 years 2 months 12 days
Approximate amount of payment delays as a percentage of the related loan balances	9.00%	11.00%	10.00%	12.00%
Weighted-average interest rate, before modification	6.50%	7.90%	6.60%	7.80%
Weighted-average interest rate, after modification	5.00%	7.20%	5.30%	7.20%
Consumer \| Home equity
Financing Receivable, Modifications
Weighted-average length of term extensions	21 years 7 months 6 days	24 years	19 years 1 month 6 days	24 years 10 months 24 days
Approximate amount of payment delays as a percentage of the related loan balances	4.00%	5.00%	6.00%	5.00%
Weighted-average interest rate, before modification	8.60%	8.80%	8.50%	8.90%
Weighted-average interest rate, after modification	7.00%	7.10%	6.90%	7.20%
Consumer \| Credit card
Financing Receivable, Modifications
Weighted-average interest rate, before modification	23.20%	23.70%	23.10%	23.90%
Weighted-average interest rate, after modification	4.10%	3.70%	4.20%	3.90%

Financing Receivable, Excluding Interest, Modified, Weighted-Average Interest Rate After Modification

No definition available.

Name:	fitb_FinancingReceivableExcludingInterestModifiedWeightedAverageInterestRateAfterModification
Namespace Prefix:	fitb_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Financing Receivable, Excluding Interest, Modified, Weighted-Average Interest Rate Before Modification

+ References

No definition available.

+ Details

Name:	fitb_FinancingReceivableExcludingInterestModifiedWeightedAverageInterestRateBeforeModification
Namespace Prefix:	fitb_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Financing Receivable, Modified, Payment Deferral, Percentage Of Related Loan Balance

+ References

No definition available.

+ Details

Name:	fitb_FinancingReceivableModifiedPaymentDeferralPercentageOfRelatedLoanBalance
Namespace Prefix:	fitb_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Financing Receivable, Modified, Weighted Average Payment Delay Increase From Modification

+ References

No definition available.

+ Details

Name:	fitb_FinancingReceivableModifiedWeightedAveragePaymentDelayIncreaseFromModification
Namespace Prefix:	fitb_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

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.

+ References

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Topic 310
-SubTopic 10
-Name Accounting Standards Codification
-Section 55
-Paragraph 12A
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481933/310-10-55-12A

Reference 2: http://fasb.org/us-gaap/role/ref/otherTransitionRef
-Topic 310
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 34
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481962/310-10-50-34

Reference 3: http://fasb.org/us-gaap/role/ref/otherTransitionRef
-Topic 310
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 33
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481962/310-10-50-33

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Topic 310
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 42
-Subparagraph (a)(2)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481962/310-10-50-42

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Topic 310
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 42
-Subparagraph (a)(1)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481962/310-10-50-42

+ Details

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

- Definition

Period of increase in weighted average maturity of financing receivable modified for debtor experiencing financial difficulty, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

+ Details

Name:	us-gaap_FinancingReceivableModifiedWeightedAverageTermIncreaseFromModification
Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Details

Name:	us-gaap_FinancingReceivablePortfolioSegmentAxis=us-gaap_CommercialPortfolioSegmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=fitb_CommercialAndIndustrialLoansMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=fitb_CommercialMortgageLoansOwnerOccupiedMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=fitb_CommercialMortgageLoansNonOwnerOccupiedMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=us-gaap_ConstructionLoansMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivablePortfolioSegmentAxis=us-gaap_ResidentialPortfolioSegmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivablePortfolioSegmentAxis=us-gaap_ConsumerPortfolioSegmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=us-gaap_HomeEquityMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=us-gaap_CreditCardReceivablesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: