Other Real Estate Owned - Components of OREO in the Consolidated Statements of Income (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2020
Real Estate Properties [Line Items]
Repairs and maintenance	$ 22	$ 85	$ 42	$ 170
Property taxes and insurance	37	16	48	149
Impairments	47	630	117	827
Net losses (gains) on OREO sales	6	(101)	(50)	(89)
Rental income	(8)	(10)	(12)	(19)
Total	104	$ 620	145	$ 1,038
Residential
Real Estate Properties [Line Items]
Amortized cost of loans in foreclosure	$ 58		$ 58		$ 1,308

Other Real Estate, Amortized Cost of Loans in Foreclosure

No definition available.

Name:	rnst_OtherRealEstateAmortizedCostOfLoansInForeclosure
Namespace Prefix:	rnst_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Other real estate owned impairments.

+ References

No definition available.

+ Details

Name:	rnst_OtherRealEstateOwnedImpairments
Namespace Prefix:	rnst_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Other real estate owned rental income.

+ References

No definition available.

+ Details

Name:	rnst_OtherRealEstateOwnedRentalIncome
Namespace Prefix:	rnst_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

The aggregate costs of keeping the property in good condition but that do not appreciably prolong the life or increase the value of the property.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03.2)
-URI http://asc.fasb.org/extlink&oid=123367319&loc=SL114868664-224227

+ Details

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

- Definition

Amount of expense recognized during the period for the foreclosure on real estate assets.

+ References

No definition available.

+ Details

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

- Definition

The net gain (loss) resulting from sales and other disposals of other real estate owned, increases (decreases) in the valuation allowance for foreclosed real estate, and write-downs of other real estate owned after acquisition or physical possession.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 220
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-04.14(d))
-URI http://asc.fasb.org/extlink&oid=120399700&loc=SL114874048-224260

+ Details

Name:	us-gaap_GainsLossesOnSalesOfOtherRealEstate
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_RealEstatePropertiesLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

The aggregate total of real estate taxes and insurance expense.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 720
-SubTopic 30
-Section 45
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=6419918&loc=d3e35301-107843

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03.6)
-URI http://asc.fasb.org/extlink&oid=123367319&loc=SL114868664-224227

+ Details

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

- Details

Name:	us-gaap_CollateralAxis=us-gaap_ResidentialRealEstateMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: