FAIR VALUE DISCLOSURES - Estimated Fair Values of Financial Instruments (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
	Mar. 31, 2024	Sep. 30, 2024	Dec. 31, 2023
Financial assets
Investment securities held-to-maturity		$ 77,985	$ 80,321
Other investments (1)		120,318	129,945
Interest Receivable		57,977	56,900
Deposits
Noninterest-bearing		3,107,699	3,317,960
Savings		4,710,223	4,331,228
Time		3,244,861	2,718,390
Federal Home Loan Bank Stock and Federal Reserve Bank Stock		$ 108,800	109,400
Servicing Assets and Servicing Liabilities at Fair Value, Assumptions Used to Estimate Fair Value, Discount Rate	11.50%	11.51%
Servicing Assets and Servicing Liabilities at Fair Value, Assumptions Used to Estimate Fair Value, Prepayment Speed	5.92%	6.16%
Impaired Commercial And Commercial Real Estate Loans Member
Deposits
Principal Amount of Commercial and Commercial Real Estate Loans		$ 26,700	19,700
Allowance for Loan and Lease Losses, Real Estate		8,100	4,400
Carrying value
Financial assets
Cash and short-term investments		851,194	1,006,019
Investment securities held-to-maturity		77,985	80,321
Other investments (1)		11,487	20,554
Loans and leases		11,394,241	10,791,743
Interest Receivable		72,147	72,620
Deposits
Deposits		13,947,754	13,360,797
Short-term borrowings		811,653	937,814
Long-term debt		344,086	344,115
Interest Payable		52,350	51,454
Fair value
Financial assets
Cash and short-term investments		851,194	1,006,019
Investment securities held-to-maturity		71,126	71,688
Other investments (1)		11,487	20,554
Loans and leases		11,348,797	10,468,144
Interest Receivable		72,147	72,620
Deposits
Deposits		13,945,883	13,347,319
Short-term borrowings		811,653	937,814
Long-term debt		343,609	350,426
Interest Payable		52,350	51,454
Fair Value, Inputs, Level 1 [Member] | Fair value
Financial assets
Cash and short-term investments		851,194	1,006,019
Investment securities held-to-maturity		0	0
Other investments (1)		1,447	1,194
Loans and leases		0	0
Interest Receivable		0	0
Deposits
Deposits		0	0
Short-term borrowings		811,653	937,814
Long-term debt		0	0
Interest Payable		8,936	15,494
Fair Value, Inputs, Level 2 [Member] | Fair value
Financial assets
Cash and short-term investments		0	0
Investment securities held-to-maturity		71,126	71,688
Other investments (1)		10,040	10,040
Loans and leases		0	0
Interest Receivable		14,170	15,697
Deposits
Deposits		13,945,883	13,347,319
Short-term borrowings		0	0
Long-term debt		343,609	350,426
Interest Payable		43,414	35,960
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 (1)		0	9,320
Loans and leases		11,348,797	10,468,144
Interest Receivable			56,923
Deposits
Deposits		0	0
Short-term borrowings		0	0
Long-term debt		0	0
Interest Payable		$ 0	$ 0