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

- Definition

Percentage of target investment allocation to total plan assets. Includes, but is not limited to, percentage on weighted-average basis if more than one plan.

+ References

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 55
-Paragraph 17
-URI http://asc.fasb.org/extlink&oid=118257860&loc=d3e4179-114921

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (d)(i)
-URI http://asc.fasb.org/extlink&oid=118255775&loc=d3e1928-114920

+ Details

Name:	us-gaap_DefinedBenefitPlanPlanAssetsTargetAllocationPercentage
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Percentage of actual investment allocation to total plan assets. Includes, but is not limited to, percentage on weighted-average basis if more than one plan.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (d)(i)
-URI http://asc.fasb.org/extlink&oid=118255775&loc=d3e1928-114920

+ Details

Name:	us-gaap_DefinedBenefitPlanWeightedAverageAssetAllocations
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Details

Name:	us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis=us-gaap_DefinedBenefitPlanEquitySecuritiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_RangeAxis=srt_MinimumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_RangeAxis=srt_MaximumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis=us-gaap_FixedIncomeSecuritiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis=fitb_AlternativeStrategiesFundMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis=us-gaap_DefinedBenefitPlanCashAndCashEquivalentsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Retirement and Benefit Plans - Targeted and Actual Weighted Average Asset Allocations by Plan Asset Category (Details)	Dec. 31, 2020	Dec. 31, 2019
Defined Benefit Plan Disclosure
Actual weighted-average asset allocation percentage	100.00%	100.00%
Equity securities
Defined Benefit Plan Disclosure
Actual weighted-average asset allocation percentage	3.00%	19.00%
Equity securities \| Lower limit
Defined Benefit Plan Disclosure
Target allocation percentage	0.00%
Equity securities \| Upper Limit
Defined Benefit Plan Disclosure
Target allocation percentage	55.00%
Fixed-income securities
Defined Benefit Plan Disclosure
Actual weighted-average asset allocation percentage	90.00%	59.00%
Fixed-income securities \| Lower limit
Defined Benefit Plan Disclosure
Target allocation percentage	50.00%
Fixed-income securities \| Upper Limit
Defined Benefit Plan Disclosure
Target allocation percentage	100.00%
Alternative strategies
Defined Benefit Plan Disclosure
Actual weighted-average asset allocation percentage	0.00%	0.00%
Alternative strategies \| Lower limit
Defined Benefit Plan Disclosure
Target allocation percentage	0.00%
Alternative strategies \| Upper Limit
Defined Benefit Plan Disclosure
Target allocation percentage	5.00%
Cash or cash equivalents
Defined Benefit Plan Disclosure
Actual weighted-average asset allocation percentage	7.00%	22.00%
Cash or cash equivalents \| Lower limit
Defined Benefit Plan Disclosure
Target allocation percentage	0.00%
Cash or cash equivalents \| Upper Limit
Defined Benefit Plan Disclosure
Target allocation percentage	100.00%