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, 2019 USD ($) loan	Jun. 30, 2018 USD ($) loan	Jun. 30, 2019 USD ($) loan	Jun. 30, 2018 USD ($) loan
Restructured loans
Number of Loans \| loan	5	1	5	5
Pre- Modification Outstanding Recorded Investment	$ 492	$ 49	$ 492	$ 708
Post- Modification Outstanding Recorded Investment	$ 489	$ 49	$ 489	$ 703
Commercial Loan
Restructured loans
Number of Loans \| loan	2		2
Pre- Modification Outstanding Recorded Investment	$ 187		$ 187
Post- Modification Outstanding Recorded Investment	$ 185		$ 185
Real estate – 1-4 family mortgage
Restructured loans
Number of Loans \| loan	3	1	3	4
Pre- Modification Outstanding Recorded Investment	$ 305	$ 49	$ 305	$ 625
Post- Modification Outstanding Recorded Investment	$ 304	$ 49	$ 304	$ 625
Real estate – commercial mortgage
Restructured loans
Number of Loans \| loan				1
Pre- Modification Outstanding Recorded Investment				$ 83
Post- Modification Outstanding Recorded Investment				$ 78

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=118936363&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_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=rnst_CommercialResidentialMortgageMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: