Other Real Estate Owned - (Details 2) - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2017	Mar. 31, 2016
Components of other real estate owned in the Consolidated Statements of Income
Repairs and maintenance	$ 197	$ 197
Property taxes and insurance	332	470
Impairments	378	294
Net (gains) losses on OREO sales	(327)	50
Rental income	(48)	(54)
Total	$ 532	$ 957

Components of other real estate owned.

No definition available.

Name:	rnst_ComponentsOfOtherRealEstateOwnedTableAbstract
Namespace Prefix:	rnst_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- 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

+ 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://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 225
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-04.14(d))
-URI http://asc.fasb.org/extlink&oid=6879574&loc=d3e536633-122882

+ Details

Name:	us-gaap_GainsLossesOnSalesOfOtherRealEstate
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

The aggregate total of real estate taxes and insurance expense.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 225
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03.6)
-URI http://asc.fasb.org/extlink&oid=63488584&loc=d3e20235-122688

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-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

+ Details

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