Allowance For Credit Losses (Loans By Class Modified In TDR) (Details) $ in Millions	12 Months Ended
Dec. 31, 2019 USD ($) obligor	Dec. 31, 2018 USD ($) obligor
Financing Receivable, Modifications [Line Items]
Number of Obligors \| obligor	543	627
Financing Receivable, Modifications, Post-Modification Recorded Investment	$ 374	$ 513
Increase in Allowance at Modification	$ 9	$ 12
Commercial And Industrial [Member]
Financing Receivable, Modifications [Line Items]
Number of Obligors \| obligor	97	113
Financing Receivable, Modifications, Post-Modification Recorded Investment	$ 259	$ 353
Increase in Allowance at Modification	$ 3	$ 5
Commercial Real Estate Mortgage - Owner-Occupied [Member]
Financing Receivable, Modifications [Line Items]
Number of Obligors \| obligor	51	67
Financing Receivable, Modifications, Post-Modification Recorded Investment	$ 29	$ 42
Increase in Allowance at Modification	$ 0	$ 0
Commercial Real Estate Construction - Owner-Occupied [Member]
Financing Receivable, Modifications [Line Items]
Number of Obligors \| obligor	1	1
Financing Receivable, Modifications, Post-Modification Recorded Investment	$ 2	$ 2
Increase in Allowance at Modification	$ 0	$ 0
Commercial investor real estate mortgage [Member]
Financing Receivable, Modifications [Line Items]
Number of Obligors \| obligor	12	25
Financing Receivable, Modifications, Post-Modification Recorded Investment	$ 26	$ 76
Increase in Allowance at Modification	$ 0	$ 3
Commercial Investor Real Estate Construction [Member]
Financing Receivable, Modifications [Line Items]
Number of Obligors \| obligor	12
Financing Receivable, Modifications, Post-Modification Recorded Investment	$ 18
Increase in Allowance at Modification	$ 2
Residential First Mortgage [Member]
Financing Receivable, Modifications [Line Items]
Number of Obligors \| obligor	159	184
Financing Receivable, Modifications, Post-Modification Recorded Investment	$ 32	$ 31
Increase in Allowance at Modification	$ 4	$ 4
Home Equity [Member]
Financing Receivable, Modifications [Line Items]
Number of Obligors \| obligor	99	106
Financing Receivable, Modifications, Post-Modification Recorded Investment	$ 7	$ 7
Increase in Allowance at Modification	$ 0	$ 0
Consumer Credit Card Financing Receivable [Member]
Financing Receivable, Modifications [Line Items]
Number of Obligors \| obligor	37	54
Financing Receivable, Modifications, Post-Modification Recorded Investment	$ 0	$ 1
Increase in Allowance at Modification	$ 0	$ 0
Indirect-vehicles and other consumer [Member]
Financing Receivable, Modifications [Line Items]
Number of Obligors \| obligor	75	77
Financing Receivable, Modifications, Post-Modification Recorded Investment	$ 1	$ 1
Increase in Allowance at Modification	$ 0	$ 0
Commercial Portfolio Segment [Member]
Financing Receivable, Modifications [Line Items]
Number of Obligors \| obligor	149	181
Financing Receivable, Modifications, Post-Modification Recorded Investment	$ 290	$ 397
Increase in Allowance at Modification	$ 3	$ 5
Total Investor Real Estate [Member]
Financing Receivable, Modifications [Line Items]
Number of Obligors \| obligor	24	25
Financing Receivable, Modifications, Post-Modification Recorded Investment	$ 44	$ 76
Increase in Allowance at Modification	$ 2	$ 3
Consumer Portfolio Segment [Member]
Financing Receivable, Modifications [Line Items]
Number of Obligors \| obligor	370	421
Financing Receivable, Modifications, Post-Modification Recorded Investment	$ 40	$ 40
Increase in Allowance at Modification	$ 4	$ 4

Amount of other addition (reduction) in allowance reserve for credit loss.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 15
-URI http://asc.fasb.org/extlink&oid=84173941&loc=d3e5212-111524

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03.7(d))
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

+ Details

Name:	us-gaap_AllowanceForLoanAndLeaseLossesAdjustmentsNet
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
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_FinancingReceivableModificationsLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Number of financing receivables that have been modified by troubled debt restructurings.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 33
-URI http://asc.fasb.org/extlink&oid=84173941&loc=SL6953676-111524

+ Details

Name:	us-gaap_FinancingReceivableModificationsNumberOfContracts2
Namespace Prefix:	us-gaap_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

Post-modification amount of investment in financing receivables modified by troubled debt restructurings.

+ References

+ Details

Name:	us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Details

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

- Details

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

- Details

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

- Details

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

- Details

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

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=rf_ResidentialFirstMortgageMember
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:

- Details

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

- Details

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

- Details

Name:	us-gaap_FinancingReceivablePortfolioSegmentAxis=rf_TotalInvestorRealEstateMember
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: