FAIR VALUE MEASUREMENTS - Schedule of Estimated Fair Values of Financial Instruments (Details) - USD ($) $ in Thousands	Dec. 31, 2024	Dec. 31, 2023
Financial assets
Debt securities held to maturity	$ 675,053	$ 730,397
Restricted bank stock	49,930	6,000
Portfolio loans, net	7,613,683	7,559,294
Mortgage servicing rights	582,500	1,490,000
Financial liabilities
Short-term borrowings	0	12,000
Junior subordinated debt owed to unconsolidated trusts	74,815	71,993
Level 1 Inputs | Carrying Amount
Financial assets
Cash and cash equivalents	697,659	719,581
Level 1 Inputs | Fair Value
Financial assets
Cash and cash equivalents	697,659	719,581
Level 2 Inputs | Carrying Amount
Financial assets
Debt securities held to maturity	826,630	872,628
Loans held for sale	3,657	2,379
Restricted bank stock	49,930	6,000
Accrued interest receivable	45,141	45,288
Financial liabilities
Time deposits	1,490,635	1,819,274
Securities sold under agreements to repurchase	155,610	187,396
Short-term borrowings	0	12,000
Long-term debt	0	18,000
Junior subordinated debt owed to unconsolidated trusts	74,815	71,993
Accrued interest payable	21,129	28,418
Level 2 Inputs | Fair Value
Financial assets
Debt securities held to maturity	675,053	730,397
Loans held for sale	3,726	2,401
Restricted bank stock	49,930	6,000
Accrued interest receivable	45,141	45,288
Financial liabilities
Time deposits	1,481,591	1,804,905
Securities sold under agreements to repurchase	155,610	187,396
Short-term borrowings	0	12,034
Long-term debt	0	18,020
Junior subordinated debt owed to unconsolidated trusts	67,314	57,153
Accrued interest payable	21,129	28,418
Level 3 Inputs | Carrying Amount
Financial assets
Portfolio loans, net	7,613,683	7,559,294
Mortgage servicing rights	1,304	3,289
Other servicing rights	1,482	1,597
Level 3 Inputs | Carrying Amount | Subordinated Debt
Financial liabilities
Long-term debt	227,723	222,882
Level 3 Inputs | Fair Value
Financial assets
Portfolio loans, net	7,426,158	7,276,905
Mortgage servicing rights	5,627	18,079
Other servicing rights	1,591	2,062
Level 3 Inputs | Fair Value | Subordinated Debt
Financial liabilities
Long-term debt	$ 219,043	$ 200,000