FAIR VALUE DISCLOSURES - Estimated Fair Values of Financial Instruments (Details) - USD ($) $ in Thousands	Mar. 31, 2023	Dec. 31, 2022
Financial assets
Investment securities held-to-maturity	$ 83,070	$ 84,021
Other investments	143,606	143,160
Loans held for sale	9,300	7,900
Interest Receivable	49,073	47,500
Deposits
Noninterest-bearing	3,830,102	4,135,180
Savings	3,746,403	3,828,139
Time	2,336,368	1,700,705
Impaired Commercial And Commercial Real Estate Loans Member
Deposits
Principal Amount of Commercial and Commercial Real Estate Loans	9,700	11,900
Allowance for Loan and Lease Losses, Real Estate	4,000	3,700
Carrying value
Financial assets
Cash and short-term investments	505,300	595,683
Investment securities held-to-maturity	83,070	84,021
Other investments	143,606	143,160
Loans and leases	10,291,794	10,165,994
Interest Receivable	65,006	63,721
Deposits
Deposits	12,674,684	12,701,177
Short-term borrowings	1,217,560	1,287,156
Long-term debt	342,647	346,672
Interest Payable	29,896	11,150
Fair value
Financial assets
Cash and short-term investments	505,300	595,683
Investment securities held-to-maturity	75,762	76,485
Other investments	143,606	143,160
Loans and leases	9,923,707	9,916,353
Interest Receivable	65,006	63,721
Deposits
Deposits	12,644,951	12,670,747
Short-term borrowings	1,217,560	1,287,156
Long-term debt	344,131	348,041
Interest Payable	29,896	11,150
Fair Value, Inputs, Level 1 [Member] | Fair value
Financial assets
Cash and short-term investments	505,300	595,683
Investment securities held-to-maturity	0	0
Other investments	1,076	1,171
Loans and leases	0	0
Interest Receivable	0	0
Deposits
Deposits	0	0
Short-term borrowings	1,217,560	1,287,156
Long-term debt	0	0
Interest Payable	8,671	3,835
Fair Value, Inputs, Level 2 [Member] | Fair value
Financial assets
Cash and short-term investments	0	0
Investment securities held-to-maturity	75,762	76,485
Other investments	133,159	132,853
Loans and leases	0	0
Interest Receivable	15,933	16,233
Deposits
Deposits	12,644,951	12,670,747
Short-term borrowings	0	0
Long-term debt	344,131	348,041
Interest Payable	21,225	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	9,371	9,136
Loans and leases	9,923,707	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