FAIR VALUE MEASUREMENTS - Schedule of Estimated Fair Values of Financial Instruments (Details) - USD ($) $ in Thousands	Dec. 31, 2025	Dec. 31, 2024
Financial assets
Debt securities held to maturity	$ 625,957	$ 675,053
Restricted bank stock	77,006	49,930
Portfolio loans, net	13,393,776	7,613,683
Mortgage servicing rights	667,900	582,500
Financial liabilities
Junior subordinated debt owed to unconsolidated trusts	77,328	74,815
Level 1 Inputs | Carrying Amount
Financial assets
Cash and cash equivalents	294,052	697,659
Level 1 Inputs | Fair Value
Financial assets
Cash and cash equivalents	294,052	697,659
Level 2 Inputs | Carrying Amount
Financial assets
Debt securities held to maturity	746,385	826,630
Loans held for sale	5,752	3,657
Restricted bank stock	77,006	49,930
Accrued interest receivable	71,788	45,141
Financial liabilities
Time deposits	2,429,890	1,490,635
Securities sold under agreements to repurchase	166,929	155,610
Junior subordinated debt owed to unconsolidated trusts	77,328	74,815
Accrued interest payable	25,372	21,129
Level 2 Inputs | Carrying Amount | Long-term borrowings
Financial liabilities
Long-term borrowings and Subordinated notes, net of unamortized issuance costs	113,806	0
Level 2 Inputs | Fair Value
Financial assets
Debt securities held to maturity	625,957	675,053
Loans held for sale	5,886	3,726
Restricted bank stock	77,006	49,930
Accrued interest receivable	71,788	45,141
Financial liabilities
Time deposits	2,425,290	1,481,591
Securities sold under agreements to repurchase	166,929	155,610
Junior subordinated debt owed to unconsolidated trusts	71,407	67,314
Accrued interest payable	25,372	21,129
Level 2 Inputs | Fair Value | Long-term borrowings
Financial liabilities
Long-term borrowings and Subordinated notes, net of unamortized issuance costs	113,853	0
Level 3 Inputs | Carrying Amount
Financial assets
Portfolio loans, net	13,393,776	7,613,683
Mortgage servicing rights	1,459	1,304
Other servicing rights	2,086	1,482
Level 3 Inputs | Carrying Amount | Subordinated Debt
Financial liabilities
Long-term borrowings and Subordinated notes, net of unamortized issuance costs	99,395	227,723
Level 3 Inputs | Fair Value
Financial assets
Portfolio loans, net	13,472,907	7,426,158
Mortgage servicing rights	5,176	5,627
Other servicing rights	2,193	1,591
Level 3 Inputs | Fair Value | Subordinated Debt
Financial liabilities
Long-term borrowings and Subordinated notes, net of unamortized issuance costs	$ 94,500	$ 219,043