SECURITIES - Securities Available for Sale (Details) - USD ($)	6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Dec. 31, 2022
Amortized cost and estimated fair value of debt securities available-for-sale
Amortized Cost	$ 700,253,000		$ 729,198,000
Unrealized Gains	113,000		157,000
Unrealized Losses	96,053,000		96,766,000
Allowance for Credit Losses	0
Estimated Fair Value	604,313,000		632,589,000
Amortized Cost
Within one year	5,804,000
After one, but within five years	103,670,000
After five, but within ten years	17,531,000
After ten years	469,000
Total	127,474,000
Total	700,253,000		729,198,000
Fair Value
Within one year	5,732,000
After one, but within five years	94,774,000
After five, but within ten years	13,698,000
After ten years	448,000
Total	114,652,000
Total	604,313,000		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	62,156,000		61,800,000
Unrealized Gains	0		0
Unrealized Losses	5,959,000		6,225,000
Allowance for Credit Losses	0
Estimated Fair Value	56,197,000		55,574,000
Amortized Cost
Total	62,156,000		61,800,000
Fair Value
Total	56,197,000		55,574,000
Mortgage-backed securities, residential
Amortized cost and estimated fair value of debt securities available-for-sale
Amortized Cost	497,995,000		518,838,000
Unrealized Gains	0		0
Unrealized Losses	80,630,000		83,707,000
Allowance for Credit Losses	0
Estimated Fair Value	417,365,000		435,131,000
Amortized Cost
Without single maturity date	497,995,000
Total	497,995,000		518,838,000
Fair Value
Without single maturity date	417,365,000
Total	417,365,000		435,131,000
Obligations of states and political subdivisions
Amortized cost and estimated fair value of debt securities available-for-sale
Amortized Cost	39,568,000		39,828,000
Unrealized Gains	1,000		2,000
Unrealized Losses	985,000		938,000
Allowance for Credit Losses	0
Estimated Fair Value	38,584,000		38,892,000
Amortized Cost
Total	39,568,000		39,828,000
Fair Value
Total	38,584,000		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	5,879,000		3,780,000
Allowance for Credit Losses	0
Estimated Fair Value	19,871,000		21,970,000
Amortized Cost
Total	25,750,000		25,750,000
Fair Value
Total	19,871,000		21,970,000
SBA loan pools
Amortized cost and estimated fair value of debt securities available-for-sale
Amortized Cost	74,784,000		82,982,000
Unrealized Gains	112,000		155,000
Unrealized Losses	2,600,000		2,116,000
Allowance for Credit Losses	0
Estimated Fair Value	72,296,000		81,022,000
Amortized Cost
Without single maturity date	74,784,000
Total	74,784,000		82,982,000
Fair Value
Without single maturity date	72,296,000
Total	$ 72,296,000		$ 81,022,000