FAIR VALUE DISCLOSURES - Estimated Fair Values of Financial Instruments (Details) - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
Financial assets
Investment securities held-to-maturity	$ 92,597	$ 98,420
Other investments	114,563	102,971
Loans held for sale	12,700	29,500
Interest Receivable	28,213	29,500
Deposits
Noninterest-bearing	4,261,429	4,185,572
Savings	4,188,867	4,157,374
Time	1,121,966	1,330,263
Impaired Commercial And Commercial Real Estate Loans Member
Deposits
Principal Amount of Commercial and Commercial Real Estate Loans	15,000	28,800
Allowance for Loan and Lease Losses, Real Estate	6,700	9,700
Carrying value
Financial assets
Cash and short-term investments	457,575	434,842
Investment securities held-to-maturity	92,597	98,420
Other investments	114,563	102,971
Loans and leases	9,117,487	9,156,307
Interest Receivable	42,623	44,627
Deposits
Deposits	12,818,908	12,871,954
Short-term borrowings	185,000	296,203
Long-term debt	379,840	409,832
Interest Payable	4,662	4,498
Fair value
Financial assets
Cash and short-term investments	457,575	434,842
Investment securities held-to-maturity	90,001	99,898
Other investments	114,563	102,971
Loans and leases	9,074,978	9,172,111
Interest Receivable	42,623	44,627
Deposits
Deposits	12,807,327	12,869,567
Short-term borrowings	185,000	296,203
Long-term debt	381,097	411,569
Interest Payable	4,662	4,498
Fair Value, Inputs, Level 1 [Member] | Fair value
Financial assets
Cash and short-term investments	457,575	434,842
Investment securities held-to-maturity	0	0
Other investments	1,133	1,331
Loans and leases	0	0
Interest Receivable	0	0
Deposits
Deposits	0	0
Short-term borrowings	185,000	296,203
Long-term debt	0	0
Interest Payable	25	0
Fair Value, Inputs, Level 2 [Member] | Fair value
Financial assets
Cash and short-term investments	0	0
Investment securities held-to-maturity	90,001	99,898
Other investments	103,815	92,025
Loans and leases	0	0
Interest Receivable	14,410	15,170
Deposits
Deposits	12,807,327	12,869,567
Short-term borrowings	0	0
Long-term debt	381,097	411,569
Interest Payable	4,637	4,498
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	9,615	9,615
Loans and leases	9,074,978	9,172,111
Interest Receivable		29,457
Deposits
Deposits	0	0
Short-term borrowings	0	0
Long-term debt	0	0
Interest Payable	$ 0	$ 0