LOANS AND THE ALLOWANCE FOR CREDIT LOSSES - Narrative (Details) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2026 USD ($) loan	Mar. 31, 2025 loan	Dec. 31, 2025 USD ($) loan
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans (includes $2,468 and $3,182 measured at fair value, respectively)	$ 2,690,535		$ 2,649,484
Number of loans modified | loan		0
Number of loans experiencing default | loan	0	0
Number of OREO loans sold | loan			2
Gains (Losses) on Sales of Other Real Estate	$ 0		$ 500
Other real estate owned, net	$ 0		$ 3,040
Financing Receivable, Number of Loans Secured by Real Estate in Foreclosure Process | loan	0		0
Accrued interest receivable	$ 10,600		$ 10,400
Significant Unobservable Inputs (Level 3)
Financing Receivable, Allowance for Credit Loss [Line Items]
Allowance for credit loss on non-performing loans	2,600		3,300
Consumer and other
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans (includes $2,468 and $3,182 measured at fair value, respectively)	22,546		22,778
Cash, securities, and other
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans (includes $2,468 and $3,182 measured at fair value, respectively)	164,117		164,726
Commercial and industrial
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans (includes $2,468 and $3,182 measured at fair value, respectively)	248,006		225,281
Owner occupied CRE
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans (includes $2,468 and $3,182 measured at fair value, respectively)	211,198		204,078
Simmons Bank
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans (includes $2,468 and $3,182 measured at fair value, respectively)	$ 116,300		$ 121,300