Non Purchased Loans - Impact of Modifications Classified as Restructured Loans (Details) - Non purchased loans and leases $ in Thousands	12 Months Ended
Dec. 31, 2021 USD ($) loan	Dec. 31, 2020 USD ($) loan	Dec. 31, 2019 USD ($) loan
Restructured loans
Number of Loans \| loan	42	38	7
Pre-Modification Outstanding Recorded Investment	$ 11,130	$ 9,040	$ 647
Post-Modification Outstanding Recorded Investment	$ 11,150	$ 9,115	$ 644
Commercial, financial, agricultural
Restructured loans
Number of Loans \| loan	7	7	2
Pre-Modification Outstanding Recorded Investment	$ 5,258	$ 1,862	$ 187
Post-Modification Outstanding Recorded Investment	$ 5,258	$ 1,859	$ 185
Real estate – 1-4 family mortgage:
Restructured loans
Number of Loans \| loan		23	5
Pre-Modification Outstanding Recorded Investment		$ 3,736	$ 460
Post-Modification Outstanding Recorded Investment		$ 3,866	$ 459
Real estate – 1-4 family mortgage: \| Primary
Restructured loans
Number of Loans \| loan	34	20
Pre-Modification Outstanding Recorded Investment	$ 5,035	$ 3,594
Post-Modification Outstanding Recorded Investment	$ 5,082	$ 3,659
Real estate – 1-4 family mortgage: \| Rental/investment
Restructured loans
Number of Loans \| loan		3
Pre-Modification Outstanding Recorded Investment		$ 142
Post-Modification Outstanding Recorded Investment		$ 207
Real estate – commercial mortgage
Restructured loans
Number of Loans \| loan		6
Pre-Modification Outstanding Recorded Investment		$ 3,418
Post-Modification Outstanding Recorded Investment		$ 3,369
Real estate – commercial mortgage \| Owner-occupied
Restructured loans
Number of Loans \| loan		3
Pre-Modification Outstanding Recorded Investment		$ 3,019
Post-Modification Outstanding Recorded Investment		$ 2,970
Real estate – commercial mortgage \| Non-owner occupied
Restructured loans
Number of Loans \| loan	1	2
Pre-Modification Outstanding Recorded Investment	$ 837	$ 210
Post-Modification Outstanding Recorded Investment	$ 810	$ 210
Real estate – commercial mortgage \| Land development
Restructured loans
Number of Loans \| loan		1
Pre-Modification Outstanding Recorded Investment		$ 189
Post-Modification Outstanding Recorded Investment		$ 189
Installment loans to individuals
Restructured loans
Number of Loans \| loan		2
Pre-Modification Outstanding Recorded Investment		$ 24
Post-Modification Outstanding Recorded Investment		$ 21

Troubled Debt Restructuring Financing Receivable Modifications [Abstract]

No definition available.

Name:	rnst_TroubledDebtRestructuringFinancingReceivableModificationsAbstract
Namespace Prefix:	rnst_
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://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 33
-URI http://asc.fasb.org/extlink&oid=123577603&loc=SL6953676-111524

+ Details

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

- Definition

Amount, after troubled debt restructuring, of modified financing receivable.

+ References

+ Details

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

- Definition

Amount, before troubled debt restructuring, of financing receivable to be modified.

+ References

+ Details

Name:	us-gaap_FinancingReceivableModificationsPreModificationRecordedInvestment2
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Details

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

- Details

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

- Details

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

- Details

Name:	us-gaap_ParticipatingMortgageLoansAxis=rnst_PrimaryMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_ParticipatingMortgageLoansAxis=rnst_RentalInvestmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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

- Details

Name:	us-gaap_ParticipatingMortgageLoansAxis=rnst_OwnerOccupiedMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_ParticipatingMortgageLoansAxis=rnst_NonownerOccupiedMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_ParticipatingMortgageLoansAxis=rnst_LandDevelopmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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