FAIR VALUE DISCLOSURES - Estimated Fair Values of Financial Instruments (Details) - USD ($) $ in Thousands	Sep. 30, 2023	Dec. 31, 2022
Financial assets
Investment securities held-to-maturity	$ 81,236	$ 84,021
Other investments	133,725	143,160
Loans held for sale	12,400	7,900
Interest Receivable	54,035	47,500
Deposits
Noninterest-bearing	3,438,572	4,135,180
Savings	4,023,455	3,828,139
Time	2,572,909	1,700,705
Impaired Commercial And Commercial Real Estate Loans Member
Deposits
Principal Amount of Commercial and Commercial Real Estate Loans	26,900	11,900
Allowance for Loan and Lease Losses, Real Estate	7,500	3,700
Carrying value
Financial assets
Cash and short-term investments	673,202	595,683
Investment securities held-to-maturity	81,326	84,021
Other investments	133,725	143,160
Loans and leases	10,501,618	10,165,994
Interest Receivable	70,471	63,721
Deposits
Deposits	12,915,553	12,701,177
Short-term borrowings	974,188	1,287,156
Long-term debt	340,902	346,672
Interest Payable	51,013	11,150
Fair value
Financial assets
Cash and short-term investments	673,202	595,683
Investment securities held-to-maturity	69,845	76,485
Other investments	133,725	143,160
Loans and leases	10,135,741	9,916,353
Interest Receivable	70,471	63,721
Deposits
Deposits	12,889,572	12,670,747
Short-term borrowings	974,188	1,287,156
Long-term debt	343,815	348,041
Interest Payable	51,013	11,150
Fair Value, Inputs, Level 1 [Member] | Fair value
Financial assets
Cash and short-term investments	673,202	595,683
Investment securities held-to-maturity	0	0
Other investments	992	1,171
Loans and leases	0	0
Interest Receivable	0	0
Deposits
Deposits	0	0
Short-term borrowings	974,188	1,287,156
Long-term debt	0	0
Interest Payable	16,613	3,835
Fair Value, Inputs, Level 2 [Member] | Fair value
Financial assets
Cash and short-term investments	0	0
Investment securities held-to-maturity	69,845	76,485
Other investments	123,413	132,853
Loans and leases	0	0
Interest Receivable	16,436	16,233
Deposits
Deposits	12,889,572	12,670,747
Short-term borrowings	0	0
Long-term debt	343,815	348,041
Interest Payable	34,400	7,315
Fair Value, Inputs, Level 3 [Member] | Fair value
Financial assets
Cash and short-term investments	0	0
Investment securities held-to-maturity	0	0
Other investments	9,320	9,136
Loans and leases	10,135,741	9,916,353
Interest Receivable		47,488
Deposits
Deposits	0	0
Short-term borrowings	0	0
Long-term debt	0	0
Interest Payable	$ 0	$ 0