Non Purchased Loans - Impact of Modifications Classified as Restructured Loans (Details) - Non purchased loans and leases $ in Thousands	3 Months Ended	6 Months Ended
Jun. 30, 2020 USD ($) loan	Jun. 30, 2019 USD ($) loan	Jun. 30, 2020 USD ($) loan	Jun. 30, 2019 USD ($) loan
Restructured loans
Number of Loans \| loan	21	5	26	5
Pre- Modification Outstanding Recorded Investment	$ 5,627	$ 492	$ 6,971	$ 492
Post- Modification Outstanding Recorded Investment	$ 5,577	$ 489	$ 6,924	$ 489
Commercial, financial, agricultural
Restructured loans
Number of Loans \| loan	4	2	6	2
Pre- Modification Outstanding Recorded Investment	$ 933	$ 187	$ 1,831	$ 187
Post- Modification Outstanding Recorded Investment	$ 930	$ 185	$ 1,828	$ 185
Real estate – 1-4 family mortgage:
Restructured loans
Number of Loans \| loan	13	3	16	3
Pre- Modification Outstanding Recorded Investment	$ 1,818	$ 305	$ 2,264	$ 305
Post- Modification Outstanding Recorded Investment	$ 1,824	$ 304	$ 2,273	$ 304
Real estate – 1-4 family mortgage: \| Primary
Restructured loans
Number of Loans \| loan	12		15
Pre- Modification Outstanding Recorded Investment	$ 1,709		$ 2,155
Post- Modification Outstanding Recorded Investment	$ 1,714		$ 2,163
Real estate – 1-4 family mortgage: \| Rental/investment
Restructured loans
Number of Loans \| loan	1		1
Pre- Modification Outstanding Recorded Investment	$ 109		$ 109
Post- Modification Outstanding Recorded Investment	$ 110		$ 110
Real estate – commercial mortgage:
Restructured loans
Number of Loans \| loan	2		2
Pre- Modification Outstanding Recorded Investment	$ 2,852		$ 2,852
Post- Modification Outstanding Recorded Investment	$ 2,802		$ 2,802
Real estate – commercial mortgage: \| Owner-occupied
Restructured loans
Number of Loans \| loan	1		1
Pre- Modification Outstanding Recorded Investment	$ 2,663		$ 2,663
Post- Modification Outstanding Recorded Investment	$ 2,613		$ 2,613
Real estate – commercial mortgage: \| Land development
Restructured loans
Number of Loans \| loan	1		1
Pre- Modification Outstanding Recorded Investment	$ 189		$ 189
Post- Modification Outstanding Recorded Investment	$ 189		$ 189
Installment loans to individuals
Restructured loans
Number of Loans \| loan	2		2
Pre- Modification Outstanding Recorded Investment	$ 24		$ 24
Post- Modification Outstanding Recorded Investment	$ 21		$ 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=121611835&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_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: