FAIR VALUE MEASUREMENTS - Schedule of Estimated Fair Values of Financial Instruments (Details) - USD ($) $ in Thousands	Mar. 31, 2025	Dec. 31, 2024
Financial assets
Debt securities held to maturity	$ 678,470	$ 675,053
Restricted bank stock	53,518	49,930
Portfolio loans, net	13,673,147	7,613,683
Financial liabilities
Short-term borrowings	11,209	0
Junior subordinated debt owed to unconsolidated trusts	77,117	74,815
Carrying Amount
Financial assets
Restricted bank stock	53,518	49,930
Level 1 Inputs | Carrying Amount
Financial assets
Cash and cash equivalents	1,200,292	697,659
Level 1 Inputs | Fair Value
Financial assets
Cash and cash equivalents	1,200,292	697,659
Level 2 Inputs | Carrying Amount
Financial assets
Debt securities held to maturity	815,402	826,630
Loans held for sale	7,270	3,657
Accrued interest receivable	79,673	45,141
Financial liabilities
Time deposits	3,091,076	1,490,635
Securities sold under agreements to repurchase	137,340	155,610
Short-term borrowings	11,209	0
Long-term debt	78,542	0
Junior subordinated debt owed to unconsolidated trusts	77,117	74,815
Accrued interest payable	41,699	21,129
Level 2 Inputs | Fair Value
Financial assets
Debt securities held to maturity	678,470	675,053
Loans held for sale	7,305	3,726
Restricted bank stock	53,518	49,930
Accrued interest receivable	79,673	45,141
Financial liabilities
Time deposits	3,083,309	1,481,591
Securities sold under agreements to repurchase	137,340	155,610
Short-term borrowings	11,130	0
Long-term debt	75,092	0
Junior subordinated debt owed to unconsolidated trusts	70,492	67,314
Accrued interest payable	41,699	21,129
Level 3 Inputs | Carrying Amount
Financial assets
Portfolio loans, net	13,673,147	7,613,683
Mortgage servicing rights	1,203	1,304
Other servicing rights	2,733	1,482
Level 3 Inputs | Fair Value
Financial assets
Portfolio loans, net	13,610,565	7,426,158
Mortgage servicing rights	5,311	5,627
Other servicing rights	2,883	1,591
Level 3 Inputs | Subordinated Debt | Carrying Amount
Financial liabilities
Long-term debt	227,967	227,723
Level 3 Inputs | Subordinated Debt | Fair Value
Financial liabilities
Long-term debt	$ 220,355	$ 219,043