Summary of Significant Policies (Summary of Significant Accounting and Reporting Policies - Additional Information) (Detail) $ in Millions	Dec. 31, 2017 USD ($)
Significant Accounting Policies
Established threshold impaired loans on accrual status	$ 1
Larger commercial loans, subject to impairment review	1
Established threshold commercial loans not subject to specific allowance calculations	1
Deferred gains on sale-leaseback transactions	$ 11

Credit Risk Related Contingent Features, Collateral Threshold

No definition available.

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- References

No definition available.

+ Details

Name:	fitb_ImpairedLoansAccrualStatus
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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Reflects the adjusted carrying amount of loans for which it is probable, based on current facts and circumstances, that a creditor will not initially be able to collect all amounts due according to the contractual terms of the loan agreement, or will not recover the previously reported carrying amount of the loan.

+ References

No definition available.

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- 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

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- Definition

The amount of the gain recorded in connection with the transaction involving the sale of property to another party and the lease of the property back to the seller to be recognized in future periods.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 840
-SubTopic 40
-Section 25
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=6456126&loc=d3e49567-112750

+ Details

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