Fair Value Measurements (Details 1) (USD $) In Thousands, unless otherwise specified	3 Months Ended	6 Months Ended
Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Reconciliation for assets and liabilities measured at fair value on a recurring basis
Beginning Balance	$ 16,162	$ 15,526	$ 15,068	$ 15,022
Realized gains (losses) included in net income	0	(14)	0	(14)
Unrealized gains (losses) included in other comprehensive income	84	(78)	1,794	1,378
Reclassification adjustment		0
Purchases	0	0	0	(952)
Sales	0	0	0	0
Issues	0	0	0	0
Settlements	(118)	0	0	0
Transfers into Level 3	0	0	(902)	0
Transfers out of Level 3	0	0	0	0
Ending Balance	15,960	15,462	15,960	15,462
Trust preferred securities [Member]
Reconciliation for assets and liabilities measured at fair value on a recurring basis
Beginning Balance	16,162	12,866	15,068	12,785
Realized gains (losses) included in net income	0	0	0	0
Unrealized gains (losses) included in other comprehensive income	84	(194)	1,794	839
Reclassification adjustment		0
Purchases	0	0	0	(952)
Sales	0	0	0	0
Issues	0	0	0	0
Settlements	(118)	0	0	0
Transfers into Level 3	0	0	(902)	0
Transfers out of Level 3	0	0	0	0
Ending Balance	15,960	12,672	15,960	12,672
Other equity securities [Member]
Reconciliation for assets and liabilities measured at fair value on a recurring basis
Beginning Balance	0	2,660	0	2,237
Realized gains (losses) included in net income	0	(14)	0	(14)
Unrealized gains (losses) included in other comprehensive income	0	116	0	539
Reclassification adjustment		0
Purchases	0	0	0	0
Sales	0	0	0	0
Issues	0	0	0	0
Settlements	0	0	0	0
Transfers into Level 3	0	0	0	0
Transfers out of Level 3	0	0	0	0
Ending Balance	$ 0	$ 2,790	$ 0	$ 2,790

Fair value measurement with unobservable inputs reconciliation recurring basis asset reclassification adjustment.

No definition available.

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Namespace Prefix:	rnst_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
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- Definition

This item represents the amount of the total realized and unrealized gains or losses for the period which are included in the statement of income (or changes in net assets) in trading revenues; the fair value of which assets was or is measured on a recurring basis using significant unobservable inputs (Level 3).

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 820

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (c)(1)

-URI http://asc.fasb.org/extlink&oid=7578670&loc=d3e19207-110258

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 157

-Paragraph 32

-Subparagraph c(1)

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

+ Details

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Data Type:	xbrli:monetaryItemType
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Period Type:	duration

- Definition

Amount of gain (loss) recognized in other comprehensive income, arising from assets measured at fair value on a recurring basis using unobservable inputs (level 3).

+ References

+ Details

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Data Type:	xbrli:monetaryItemType
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- Definition

Issues that have taken place during the period in relation to assets measured at fair value and categorized within Level 3 of the fair value hierarchy.

+ References

+ Details

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- Definition

Purchases that have taken place during the period in relation to assets measured at fair value and categorized within Level 3 of the fair value hierarchy.

+ References

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Sales that have taken place during the period in relation to assets measured at fair value and categorized within Level 3 of the fair value hierarchy.

+ References

+ Details

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- Definition

Settlements that have taken place during the period in relation to assets measured at fair value and categorized within Level 3 of the fair value hierarchy.

+ References

+ Details

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Balance Type:	credit
Period Type:	duration

- Definition

Transfers into assets measured at fair value and categorized within Level 3 of the fair value hierarchy that have taken place during the period.

+ References

+ Details

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Period Type:	duration

- Definition

Transfers out of assets measured at fair value and categorized within Level 3 of the fair value hierarchy that have taken place during the period.

+ References

+ Details

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

- Definition

This element represents an asset measured at fair value using significant unobservable inputs (Level 3) which is required for reconciliation purposes of beginning and ending balances.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 820

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (c)

-URI http://asc.fasb.org/extlink&oid=7578670&loc=d3e19207-110258

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 157

-Paragraph 32

-Subparagraph c

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

+ Details

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