FAIR VALUE MEASUREMENTS - Fair Values and Carrying Amounts (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Financial Assets
Securities available for sale	$ 545,327	$ 585,046
Level 1
Financial Assets
Cash and cash equivalents	341,199	226,007
Securities available for sale	0
FHLB stock	0
Loans held for sale	0
Net loans	0
Accrued interest receivable	0
Cash surrender value of bank-owned life insurance policies	0
Derivative assets	0
Financial Liabilities
Securities sold under agreements to repurchase	0
FHLB advances	0
Derivative liabilities	0
Level 1 | Bank Non-maturity Deposits [Member]
Financial Liabilities
Non-maturity deposits	0
Level 1 | Bank Time Deposits [Member]
Financial Liabilities
Non-maturity deposits	0
Level 1 | Subordinated borrowings
Financial Liabilities
Subordinated borrowings	0
Level 2
Financial Assets
Cash and cash equivalents	0
Securities available for sale	545,327	585,046
FHLB stock	10,192	14,036
Loans held for sale	0
Net loans	0
Accrued interest receivable	3,272	2,964
Cash surrender value of bank-owned life insurance policies	79,380	77,870
Derivative assets	16,972	25,917
Financial Liabilities
Short-term other borrowings		27,779
Securities sold under agreements to repurchase	21,667
FHLB advances	169,815	252,698
Derivative liabilities	18,159	31,443
Level 2 | Bank Non-maturity Deposits [Member]
Financial Liabilities
Non-maturity deposits	2,452,990	2,122,222
Level 2 | Bank Time Deposits [Member]
Financial Liabilities
Non-maturity deposits	470,000	694,700
Level 2 | Subordinated borrowings
Financial Liabilities
Subordinated borrowings	63,660	57,091
Level 3
Financial Assets
Cash and cash equivalents	0
Securities available for sale	0
FHLB stock	0
Loans held for sale	7,505	24,163
Net loans	2,472,108	2,547,970
Accrued interest receivable	0
Cash surrender value of bank-owned life insurance policies	0
Derivative assets	47	22
Financial Liabilities
Securities sold under agreements to repurchase	0
FHLB advances	0
Derivative liabilities	140	95
Level 3 | Bank Non-maturity Deposits [Member]
Financial Liabilities
Non-maturity deposits	0
Level 3 | Bank Time Deposits [Member]
Financial Liabilities
Non-maturity deposits	0
Level 3 | Subordinated borrowings
Financial Liabilities
Subordinated borrowings	0
Carrying Amount
Financial Assets
Cash and cash equivalents	341,199	226,007
Securities available for sale	545,327	585,046
FHLB stock	10,192	14,036
Loans held for sale	7,505	23,988
Net loans	2,511,706	2,543,803
Accrued interest receivable	3,272	2,964
Cash surrender value of bank-owned life insurance policies	79,380	77,870
Derivative assets	17,019	28,895
Financial Liabilities
Short-term other borrowings		27,779
Securities sold under agreements to repurchase	21,667
FHLB advances	168,600	248,283
Derivative liabilities	18,299	31,348
Carrying Amount | Bank Non-maturity Deposits [Member]
Financial Liabilities
Non-maturity deposits	2,538,044	2,207,854
Carrying Amount | Bank Time Deposits [Member]
Financial Liabilities
Non-maturity deposits	469,221	698,361
Carrying Amount | Subordinated borrowings
Financial Liabilities
Subordinated borrowings	60,083	59,961
Total Fair Value
Financial Assets
Cash and cash equivalents	341,199	226,007
Securities available for sale	545,327	585,046
FHLB stock	10,192	14,036
Loans held for sale	7,505	24,163
Net loans	2,472,108	2,547,970
Accrued interest receivable	3,272	2,964
Cash surrender value of bank-owned life insurance policies	79,380	77,870
Derivative assets	17,019	25,895
Financial Liabilities
Short-term other borrowings		27,779
Securities sold under agreements to repurchase	21,667
FHLB advances	169,815	252,698
Derivative liabilities	18,299	31,348
Total Fair Value | Bank Non-maturity Deposits [Member]
Financial Liabilities
Non-maturity deposits	2,452,990	2,122,222
Total Fair Value | Bank Time Deposits [Member]
Financial Liabilities
Non-maturity deposits	470,000	694,700
Total Fair Value | Subordinated borrowings
Financial Liabilities
Subordinated borrowings	$ 63,660	$ 57,091