COMMITMENTS AND CONTINGENCIES - Additional Information (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
	Mar. 31, 2025	Jun. 30, 2024	Dec. 31, 2024	Mar. 31, 2024	Jan. 01, 2024	Dec. 31, 2023
Commitments and Contingencies Disclosure [Line Items]
Reserves for unfunded commitments	$ 16,400		$ 16,900
Loans and Leases Receivable, Commitments, Fixed Rates	74,900	$ 69,300
Loans and Leases Receivable, Commitments, Variable Rates	$ 3,700,000	$ 3,700,000
Loan Commitments, Fixed Interest Rate Range, Minimum	0.00%	0.00%
Loan Commitments, Fixed Interest Rate Range, Maximum	21.00%	21.00%
Loan Commitments, Fixed Rate, Maturities, Minimum	1 year	1 year
Loan Commitments, Fixed Rate, Maturities, Maximum	31 years	31 years 7 months 6 days
Letters of credit issued to guarantee performance of a client to a third party	$ 26,000		25,100
Derivative, Notional Amount	18,232,958		16,941,027
Stockholders' Equity Attributable to Parent	2,501,235		2,438,041	$ 2,287,003		$ 2,267,974
Estimated Litigation Liability	0		0
Retained earnings
Commitments and Contingencies Disclosure [Line Items]
Stockholders' Equity Attributable to Parent	1,304,636		1,276,329	$ 1,166,065		$ 1,136,718
Cumulative Effect, Period of Adoption, Adjustment [Member] | Retained earnings
Commitments and Contingencies Disclosure [Line Items]
Stockholders' Equity Attributable to Parent					$ 600
Credit Default Swap
Commitments and Contingencies Disclosure [Line Items]
Derivative, Notional Amount	286,600		310,700
Commitments to Extend Credit
Commitments and Contingencies Disclosure [Line Items]
Commitments outstanding to extend credit	$ 3,800,000		$ 3,800,000