Nominal or face amount used to calculate payment on derivative.

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 1B
-URI http://asc.fasb.org/extlink&oid=109980867&loc=SL5580258-113959

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 1A
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=109980867&loc=SL5579245-113959

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	na
Period Type:	instant

- Definition

The number of derivative instruments of a particular group held by the entity.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 1A
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=109980867&loc=SL5579245-113959

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 1B
-URI http://asc.fasb.org/extlink&oid=109980867&loc=SL5580258-113959

+ Details

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Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Definition

Period the derivative contract is outstanding, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

No definition available.

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
Balance Type:	na
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

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Period Type:	duration

- Details

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Namespace Prefix:
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- Details

Name:	us-gaap_DerivativeInstrumentRiskAxis=rnst_OffsettingInterestRateContractsWithOtherFinancialInstitutionsMember
Namespace Prefix:
Data Type:	na
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- Details

Name:	us-gaap_DerivativeInstrumentRiskAxis=us-gaap_InterestRateSwapMember
Namespace Prefix:
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- Details

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- Details

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- Details

Name:	us-gaap_DerivativeInstrumentRiskAxis=rnst_CommitmentsToFundFixedRateResidentialMortgageLoansMember
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Data Type:	na
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- Details

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Derivative Instruments - Additional Information (Details) $ in Thousands	1 Months Ended
	Jun. 30, 2014 USD ($) derivative_instrument	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Apr. 30, 2018 USD ($)	Apr. 30, 2012 USD ($) derivative_instrument
Interest rate contracts with corporate customers
Derivatives, Fair Value [Line Items]
Notional amount		$ 219,664
Offsetting interest rate contracts with other financial institutions
Derivatives, Fair Value [Line Items]
Notional amount		219,664
Interest rate swap
Derivatives, Fair Value [Line Items]
Number of instruments held \| derivative_instrument	2
Floating rate liability at the bank level, derivative one
Derivatives, Fair Value [Line Items]
Notional amount	$ 15,000
Term of contract	4 years
Floating rate liability at the bank level, derivative two
Derivatives, Fair Value [Line Items]
Term of contract	5 years
Cash Flow Hedging
Derivatives, Fair Value [Line Items]
Notional amount				$ 30,000	$ 32,000
Number of instruments held \| derivative_instrument					2
Commitments to fund fixed-rate residential mortgage loans
Derivatives, Fair Value [Line Items]
Notional amount		215,751	$ 159,464
Commitments to sell residential mortgage loans
Derivatives, Fair Value [Line Items]
Notional amount		$ 414,000	$ 281,343