Long-term Debt LT Debt Interest Rates (Details) - USD ($) $ in Thousands		Nov. 14, 2025	Aug. 10, 2007	Aug. 08, 2007	May 20, 2005		Sep. 04, 2003	Sep. 30, 2022		Dec. 31, 2021		Nov. 06, 2020	Oct. 10, 2007
Debt Instrument [Line Items]
Other long-term debt	[1]							$ 60,264		$ 60,260
Southside Statutory Trust III
Debt Instrument [Line Items]
Other long-term debt							$ 20,619	20,572	[1],[2]	20,568	[1],[2]
Southside Statutory Trust III | Three-Month London Interbank Offered Rate (LIBOR)
Debt Instrument [Line Items]
Basis on variable rate							2.94%
Southside Statutory Trust IV
Debt Instrument [Line Items]
Other long-term debt				$ 23,196				23,196	[1]	23,196	[1]
Southside Statutory Trust IV | Three-Month London Interbank Offered Rate (LIBOR)
Debt Instrument [Line Items]
Basis on variable rate				1.30%
Southside Statutory Trust V
Debt Instrument [Line Items]
Other long-term debt			$ 12,887					12,887	[1]	12,887	[1]
Southside Statutory Trust V | Three-Month London Interbank Offered Rate (LIBOR)
Debt Instrument [Line Items]
Basis on variable rate			2.25%
Magnolia Trust Company I
Debt Instrument [Line Items]
Other long-term debt					$ 3,609	[3]		$ 3,609	[1]	$ 3,609	[1]		$ 3,600
Magnolia Trust Company I | Three-Month London Interbank Offered Rate (LIBOR)
Debt Instrument [Line Items]
Basis on variable rate					1.80%
3.875% Subordinated Notes
Debt Instrument [Line Items]
Debt face amount												$ 100,000
Stated interest rate								3.875%				3.875%
Forecast | 3.875% Subordinated Notes | Secured Overnight Financing Rate (SOFR) Overnight Index Swap Rate
Debt Instrument [Line Items]
Basis on variable rate		3.66%

[1] This debt consists of trust preferred securities that qualify under the risk-based capital guidelines as Tier 1 capital, subject to certain limitations.

[2] The unamortized debt issuance costs reflected in the carrying amount of the Southside Statutory Trust III junior subordinated debentures totaled $47,000 at September 30, 2022 and $51,000 at December 31, 2021.

[3] On October 10, 2007, as part of an acquisition we assumed $3.6 million of floating rate junior subordinated debentures issued in 2005 to Magnolia Trust Company I.