Significant Accounting Policies (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013
Changes in the FDIC loss-share indemnification asset
Balance at January 1	$ 26,273us-gaap_FDICIndemnificationAsset	$ 44,153us-gaap_FDICIndemnificationAsset
Additions through acquisition	0	0
Realized losses in excess of initial estimates on:
Loans	6,293	3,039
OREO	2,593	5,983
Reimbursable expenses	335	4,612
Amortization	(9,195)	(3,423)
Reimbursements received from the FDIC	(13,783)	(28,091)
Balance at December 31	$ 12,516us-gaap_FDICIndemnificationAsset	$ 26,273us-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
Namespace Prefix:	rnst_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Details

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

- Definition

Reimbursable expenses receivable from FDIC.

+ References

No definition available.

+ Details

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.

+ References

No definition available.

+ Details

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).

+ References

No definition available.

+ Details

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 acquisitions of assets relating to loss sharing agreements with the Federal Deposit Insurance Corporation (FDIC).

+ References

No definition available.

+ Details

Name:	us-gaap_FDICIndemnificationAssetAcquisitions
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.

+ References

No definition available.

+ Details

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).

+ References

No definition available.

+ Details

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