Credit Quality and the Allowance for Loan and Lease Losses - Summary of Subsequent Defaults (Details) $ in Millions	3 Months Ended	6 Months Ended
Jun. 30, 2021 USD ($) contract	Jun. 30, 2020 USD ($) contract	Jun. 30, 2021 USD ($) contract	Jun. 30, 2020 USD ($) contract
Financing Receivable, Modifications
Number of Contracts \| contract	65	58	162	313
Amortized Cost \| $	$ 2	$ 13	$ 34	$ 26
Commercial \| Commercial and industrial loans
Financing Receivable, Modifications
Number of Contracts \| contract	1	6	1	6
Amortized Cost \| $	$ 0	$ 4	$ 0	$ 4
Commercial \| Commercial mortgage owner-occupied loans
Financing Receivable, Modifications
Number of Contracts \| contract		5		7
Amortized Cost \| $		$ 1		$ 2
Commercial \| Commercial mortgage nonowner-occupied loans
Financing Receivable, Modifications
Number of Contracts \| contract		1	1	2
Amortized Cost \| $		$ 4	$ 25	$ 9
Residential Mortgage
Financing Receivable, Modifications
Number of Contracts \| contract	16	25	51	72
Amortized Cost \| $	$ 2	$ 4	$ 7	$ 10
Consumer \| Home equity
Financing Receivable, Modifications
Number of Contracts \| contract	5	2	17	3
Amortized Cost \| $	$ 0	$ 0	$ 1	$ 0
Consumer \| Indirect secured consumer loans
Financing Receivable, Modifications
Number of Contracts \| contract	32	3	58	6
Amortized Cost \| $	$ 0	$ 0	$ 1	$ 0
Consumer \| Credit card
Financing Receivable, Modifications
Number of Contracts \| contract	11	16	34	217
Amortized Cost \| $	$ 0	$ 0	$ 0	$ 1

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

- Definition

Number of financing receivable contracts modified as troubled debt restructuring within previous 12 months, with subsequent payment default.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 34
-URI http://asc.fasb.org/extlink&oid=123577603&loc=SL6953682-111524

+ Details

Name:	us-gaap_FinancingReceivableModificationsSubsequentDefaultNumberOfContracts1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of financing receivable modified as troubled debt restructuring within previous 12 months, with subsequent payment default.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 34
-Subparagraph (a)(2)
-URI http://asc.fasb.org/extlink&oid=123577603&loc=SL6953682-111524

+ Details

Name:	us-gaap_FinancingReceivableModificationsSubsequentDefaultRecordedInvestment1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
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_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_AutomobileLoanMember
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: