FDIC Loss-Share Indemnification Asset - (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
Mar. 31, 2015
FDIC Loss-Share Indemnification Asset [Abstract]
Eligible losses covered (percent)	80.00%rnst_PercentageofEligibleLossesCovered
Eligible recoveries covered (percent)	80.00%
Changes in FDIC Loss Share Indemnification Asset [Roll Forward]
Balance at January 1, 2015	$ 12,516us-gaap_FDICIndemnificationAsset
Changes in expected cash flows from initial estimates on:
Covered Loans	(1,503)
Covered OREO	(31)
Reimbursable expenses	163
Accretion	0
Reimbursements received from the FDIC	(2,211)
Balance at March 31, 2015	$ 8,934us-gaap_FDICIndemnificationAsset

Additional losses on other real estate owned.

No definition available.

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

- Details

Name:	rnst_ChangesinFDICLossShareIndemnificationAssetRollForward
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Data Type:	xbrli:stringItemType
Balance Type:	na
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- Details

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

- Details

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

- Definition

Percentage of eligible losses covered under loss-sharing agreements with the FDIC

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No definition available.

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Name:	rnst_PercentageofEligibleLossesCovered
Namespace Prefix:	rnst_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Percentage of eligible recoveries covered under loss-sharing agreements with the FDIC

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No definition available.

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Name:	rnst_PercentageofEligibleRecoveriesCovered
Namespace Prefix:	rnst_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Reimbursable expenses receivable from FDIC.

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No definition available.

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

- Definition

Carrying amount of receivable assets originating from the indemnification agreement with the Federal Deposit Insurance Corporation (FDIC), in which the FDIC is to partially cover losses.

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No definition available.

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Name:	us-gaap_FDICIndemnificationAsset
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Increases to the indemnification asset due to accretion of the loan discount relating to loss sharing agreements with the Federal Deposit Insurance Corporation (FDIC).

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No definition available.

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

- Definition

Amount of increases to the indemnification asset due to additional estimated losses assumed by the Federal Deposit Insurance Corporation (FDIC), relating to loss sharing agreements with the FDIC.

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No definition available.

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

- Definition

Amount of decreases to the indemnification asset due to cash payments received relating to loss sharing agreements with the Federal Deposit Insurance Corporation (FDIC).

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No definition available.

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