Aggregate notional amount specified by the derivative(s). Expressed as an absolute value.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Article 12
-Section 13
-Sentence Column B

+ Details

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Period Type:	instant

- Definition

Derivative instruments.

+ References

No definition available.

+ Details

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

- Definition

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

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 1B
-URI http://asc.fasb.org/extlink&oid=84234895&loc=SL5580258-113959

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 1A
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=84234895&loc=SL5579245-113959

+ Details

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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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Period Type:	duration

- Details

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- Details

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- Details

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- Details

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- Details

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- Details

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- Details

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- Details

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Derivative Instruments - Narrative (Details)	1 Months Ended
Derivative Instruments - Narrative (Details)	Jun. 30, 2014 USD ($) derivative_instrument	Mar. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Apr. 30, 2012 USD ($) derivative_instrument
Interest rate contracts with corporate customers
Derivative Instruments (Textual) [Abstract]
Notional amount		$ 212,840,000
Offsetting interest rate contracts with other financial institutions
Derivative Instruments (Textual) [Abstract]
Notional amount		212,840,000
Interest rate swaps
Derivative Instruments (Textual) [Abstract]
Number of instruments held \| derivative_instrument	2
Floating rate liability at the bank level, derivative one
Derivative Instruments (Textual) [Abstract]
Notional amount	$ 15,000,000
Term of contract	4 years
Floating rate liability at the bank level, derivative two
Derivative Instruments (Textual) [Abstract]
Notional amount	$ 15,000,000
Term of contract	5 years
Cash flow hedging
Derivative Instruments (Textual) [Abstract]
Notional amount				$ 32,000,000
Number of instruments held \| derivative_instrument				2
Commitments to fund fixed-rate residential mortgage loans
Derivative Instruments (Textual) [Abstract]
Notional amount		208,883,000	$ 131,000,000
Commitments to sell residential mortgage loans
Derivative Instruments (Textual) [Abstract]
Notional amount		$ 344,000,000	$ 199,000,000