SECURITIES - Securities Available for Sale (Details) - USD ($)	9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Dec. 31, 2022
Amortized cost and estimated fair value of debt securities available-for-sale
Amortized Cost	$ 683,837,000		$ 729,198,000
Unrealized Gains	96,000		157,000
Unrealized Losses	114,929,000		96,766,000
Allowance for Credit Losses	0
Estimated Fair Value	569,004,000		632,589,000
Amortized Cost
Within one year	5,480,000
After one, but within five years	101,840,000
After five, but within ten years	18,528,000
After ten years	470,000
Total	126,318,000
Total	683,837,000		729,198,000
Fair Value
Within one year	5,243,000
After one, but within five years	91,028,000
After five, but within ten years	14,821,000
After ten years	406,000
Total	111,498,000
Total	569,004,000		632,589,000
Proceeds from sales and calls of securities resulting in gains or losses
Debt securities, gain (loss)	0	$ 0
U.S. Treasury notes and bonds
Amortized cost and estimated fair value of debt securities available-for-sale
Amortized Cost	61,033,000		61,800,000
Unrealized Gains	0		0
Unrealized Losses	6,033,000		6,225,000
Allowance for Credit Losses	0
Estimated Fair Value	55,000,000		55,574,000
Amortized Cost
Total	61,033,000		61,800,000
Fair Value
Total	55,000,000		55,574,000
Mortgage-backed securities, residential
Amortized cost and estimated fair value of debt securities available-for-sale
Amortized Cost	486,189,000		518,838,000
Unrealized Gains	0		0
Unrealized Losses	97,158,000		83,707,000
Allowance for Credit Losses	0
Estimated Fair Value	389,031,000		435,131,000
Amortized Cost
Without single maturity date	486,189,000
Total	486,189,000		518,838,000
Fair Value
Without single maturity date	389,031,000
Total	389,031,000		435,131,000
Obligations of states and political subdivisions
Amortized cost and estimated fair value of debt securities available-for-sale
Amortized Cost	39,535,000		39,828,000
Unrealized Gains	0		2,000
Unrealized Losses	3,382,000		938,000
Allowance for Credit Losses	0
Estimated Fair Value	36,153,000		38,892,000
Amortized Cost
Total	39,535,000		39,828,000
Fair Value
Total	36,153,000		38,892,000
Corporate bonds and notes
Amortized cost and estimated fair value of debt securities available-for-sale
Amortized Cost	25,750,000		25,750,000
Unrealized Gains	0		0
Unrealized Losses	5,405,000		3,780,000
Allowance for Credit Losses	0
Estimated Fair Value	20,345,000		21,970,000
Amortized Cost
Total	25,750,000		25,750,000
Fair Value
Total	20,345,000		21,970,000
SBA loan pools
Amortized cost and estimated fair value of debt securities available-for-sale
Amortized Cost	71,330,000		82,982,000
Unrealized Gains	96,000		155,000
Unrealized Losses	2,951,000		2,116,000
Allowance for Credit Losses	0
Estimated Fair Value	68,475,000		81,022,000
Amortized Cost
Without single maturity date	71,330,000
Total	71,330,000		82,982,000
Fair Value
Without single maturity date	68,475,000
Total	$ 68,475,000		$ 81,022,000