FAIR VALUE - Summary of carrying amounts and estimated fair values for financial instruments (Details) - USD ($) $ in Thousands	Mar. 31, 2025	Dec. 31, 2024	Mar. 31, 2024	Dec. 31, 2023
Assets:
Cash and cash equivalents	$ 271,582	$ 236,041	$ 257,889	$ 254,442
Held-to-maturity securities, net of ACL	67,479	68,161
Total	2,425,367	2,425,565
Accrued interest receivable	10,623	10,364
Liabilities:
FHLB borrowings – fixed rate	51,612	57,038
Subordinated notes	44,621	52,565
Accrued interest payable	2,371	1,995
Carrying Amount
Assets:
Cash and cash equivalents	271,582	236,041
Held-to-maturity securities, net of ACL	73,775	75,724
Total	2,401,299	2,399,952
Accrued interest receivable	10,623	10,364
Liabilities:
Term deposits	379,533	471,415
Non-term deposits	2,135,864	2,042,794
FHLB borrowings – fixed rate		5,000
FHLB borrowings – floating rate		50,000
Federal Reserve borrowings – fixed rate	1,612	2,038
Accrued interest payable	2,371	1,995
Subordinated Notes | Carrying Amount
Liabilities:
Subordinated notes	44,621	52,565
Quoted Prices in Active Markets for Identical Assets (Level 1) | Carrying Amount
Liabilities:
FHLB borrowings – fixed rate		5,000
Quoted Prices in Active Markets for Identical Assets (Level 1) | Estimate of Fair Value Measurement
Assets:
Cash and cash equivalents	271,582	236,041
Held-to-maturity securities, net of ACL	245	242
Accrued interest receivable	10,623	10,364
Liabilities:
Term deposits	336,284	429,008
Non-term deposits	2,135,864	2,042,794
Federal Reserve borrowings – fixed rate	1,612	2,038
Accrued interest payable	2,371	1,995
Significant Other Observable Inputs (Level 2) | Estimate of Fair Value Measurement
Assets:
Held-to-maturity securities, net of ACL	59,056	60,044
Liabilities:
FHLB borrowings – floating rate	50,000	50,000
Federal Reserve borrowings – fixed rate	0
Significant Unobservable Inputs (Level 3) | Estimate of Fair Value Measurement
Assets:
Held-to-maturity securities, net of ACL	8,178	7,875
Total	2,332,332	2,325,081
Liabilities:
Term deposits	43,587	42,764
Significant Unobservable Inputs (Level 3) | Subordinated Notes | Estimate of Fair Value Measurement
Liabilities:
Subordinated notes	$ 40,901	$ 48,451