Related Party Transactions (Related Party Transactions - Additional Information) (Detail) - Vantiv, Inc. $ in Millions	9 Months Ended
Sep. 30, 2016 USD ($)
Related Party Transactions
Amount Of Cash Flow Sales From 2019 To 2035	$ 331
Payment From Vantiv Inc to Bancorp To Terminate And Settle Certain Remaining TRA Cash Flows	171
Potential Termination And Settlement Of Tra Cash Flows	$ 394
Tra Obligations Settled If Options Exercised 2017	10.00%
Tra Obligations Settled If Options Exercised 2018	15.00%
Other Noninterest Income
Related Party Transactions
Gain On Tax Receivable Agreement Termination And Settlement	$ 116
Pretax Gain Recognized	$ 164
Lower Limit
Related Party Transactions
Amount Of Cash Flow Sales From Years 2019 To 2035	2019
Upper Limit
Related Party Transactions
Amount Of Cash Flow Sales From Years 2019 To 2035	2035

Amount Of Cash Flow Sales From 2019 To 2035

No definition available.

Name:	fitb_Fitb_amountofcashflowsalesfrom2019to2035
Namespace Prefix:	fitb_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount Of Cash Flow Sales From Years 2019 To 2035

+ References

No definition available.

+ Details

Name:	fitb_Fitb_amountofcashflowsalesfromyears2019to2035
Namespace Prefix:	fitb_
Data Type:	xbrli:gYearItemType
Balance Type:	na
Period Type:	duration

- Definition

Gain recognized on the termination and settlement of the tax receivable agreement with Vantiv, Inc.

+ References

No definition available.

+ Details

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

- Definition

Potential payment from Vantiv, Inc. to the Bancorp to terminate and settle certain remaining TRA cash flows upon the exercise of certain call options by Vantiv, Inc. or certain put options by the Bancorp

+ References

No definition available.

+ Details

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

- Definition

Potential termination and settlement of TRA cash flows upon the exercise of certain call options by Vantiv, Inc. or certain put options by the Bancorp.

+ References

No definition available.

+ Details

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

- Definition

Pre-tax gain recognized by the Bancorp relating to call options or put options.

+ References

No definition available.

+ Details

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

- Definition

Total percentage of TRA obligations that would settle in 2017 if call options or put options are exercised

+ References

No definition available.

+ Details

Name:	fitb_Fitb_traobligationssettledifoptionsexercised2017
Namespace Prefix:	fitb_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Total percentage of TRA obligations that would settle in 2018 if call options or put options are exercised

+ References

No definition available.

+ Details

Name:	fitb_Fitb_traobligationssettledifoptionsexercised2018
Namespace Prefix:	fitb_
Data Type:	num:percentItemType
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

No definition available.

+ Details

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

- Details

Name:	us-gaap_RelatedPartyTransactionsByRelatedPartyAxis=fitb_Fitb_ftpsincmemberMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	fitb_StatementOfIncomeLocationAxis=fitb_OtherNoninterestIncomeMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RangeAxis=us-gaap_MinimumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RangeAxis=us-gaap_MaximumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: