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	Jun. 30, 2023		Jun. 14, 2023	Dec. 31, 2022		Nov. 06, 2020	Oct. 10, 2007
Debt Instrument [Line Items]
Other long-term debt	[1]							$ 60,267			$ 60,265
Southside Statutory Trust III (2)
Debt Instrument [Line Items]
Other long-term debt							$ 20,619	20,575	[1],[2]		20,573	[1],[2]
Southside Statutory Trust III (2) | Three-Month London Interbank Offered Rate (LIBOR)
Debt Instrument [Line Items]
Basis on variable rate	[3]						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	[3]			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	[3]		2.25%
Magnolia Trust Company I
Debt Instrument [Line Items]
Other long-term debt					$ 3,609	[4]		$ 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	[3],[4]				1.80%
3.875% Subordinated Notes
Debt Instrument [Line Items]
Debt face amount	[5]												$ 100,000
Stated interest rate								3.875%					3.875%
Debt instrument repurchase										$ 5,000
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 $44,000 at June 30, 2023 and $46,000 at December 31, 2022.

[3] Effective July 1, 2023, the Company began utilizing SOFR to reset rates on our floating rate trust preferred subordinated debentures, due to the fact that LIBOR ceased to be published as of June 30, 2023.

[4] 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

[5] On June 14, 2023, the Company repurchased $5.0 million of the $100 million fixed-to-floating rate subordinated notes that mature on November 15, 2030.