Condensed Financial Information (Parent Company Only) - Condensed Balance Sheets 2 (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Parent Company
Unrealized depreciation on available-for-sale securities, net of income taxes	$ (9,686)	$ (6,108)

Amount of income tax related to the accumulated appreciation or loss in value of the total of available-for-sale securities at the end of an accounting period.

No definition available.

Name:	sfnc_AccumulatedOtherComprehensiveIncomeLossAvailableForSaleSecuritiesTax
Namespace Prefix:	sfnc_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant