Summary of Significant Accounting Policies Summary of Significant Accounting Policies (Details) $ in Thousands	12 Months Ended
Dec. 31, 2017 USD ($)
Accounting Standards Update, 2018-02
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Reclassification from AOCI to retained earnings, tax effect	$ (2,046)

Amount of increase (decrease) in accumulated other comprehensive income (AOCI) for reclassification to retained earnings of tax effect from remeasurement of deferred tax pursuant to Tax Cuts and Jobs Act.

No definition available.

Name:	rnst_TaxCutsandJobsActReclassificationfromAOCItoRetainedEarningsTaxEffect
Namespace Prefix:	rnst_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration