FAIR VALUE - Assets and Liabilities Measured at Fair Value on Recurring Basis Using Significant Unobservable Inputs (Level 3) (Details) $ in Thousands	Dec. 31, 2024 USD ($)	Dec. 31, 2023 USD ($)
Available For Sale Securities [Abstract]
Available-For-Sale Securities, Debt Securities	$ 4,565,302	$ 5,229,984
Residential MBS [Member]
Available For Sale Securities [Abstract]
Available-For-Sale Securities, Debt Securities	2,481,253	2,633,161
Residential MBS [Member] | Private label [Member]
Available For Sale Securities [Abstract]
Available-For-Sale Securities, Debt Securities	4,195
Fair Value, Measurements, Recurring [Member] | Puerto Rico government obligations [Member]
Available For Sale Securities [Abstract]
Available-For-Sale Securities, Debt Securities	1,620	1,415
Fair Value, Measurements, Recurring [Member] | Fair Value Inputs Level 3 [Member] | Residential MBS [Member] | Private label [Member] | Valuation Technique, Discounted Cash Flow [Member]
Available For Sale Securities [Abstract]
Available-For-Sale Securities, Debt Securities	4,195	4,785
Fair Value, Measurements, Recurring [Member] | Fair Value Inputs Level 3 [Member] | Puerto Rico government obligations [Member]
Available For Sale Securities [Abstract]
Available-For-Sale Securities, Debt Securities	1,620	1,415
Fair Value, Measurements, Recurring [Member] | Fair Value Inputs Level 3 [Member] | Puerto Rico government obligations [Member] | Valuation Technique, Discounted Cash Flow [Member]
Available For Sale Securities [Abstract]
Available-For-Sale Securities, Debt Securities	$ 1,620	$ 1,415
Fair Value, Measurements, Recurring [Member] | Fair Value Inputs Level 3 [Member] | Minimum [Member] | Residential MBS [Member] | Private label [Member] | Measurement Input, Discount Rate [Member]
Available For Sale Securities [Abstract]
Debt Securities, Available-for-sale, Measurement Input	0.166	0.161
Fair Value, Measurements, Recurring [Member] | Fair Value Inputs Level 3 [Member] | Minimum [Member] | Residential MBS [Member] | Private label [Member] | Measurement Input, Constant Prepayment Rate [Member]
Available For Sale Securities [Abstract]
Debt Securities, Available-for-sale, Measurement Input	0.000	0.000
Fair Value, Measurements, Recurring [Member] | Fair Value Inputs Level 3 [Member] | Minimum [Member] | Residential MBS [Member] | Private label [Member] | Measurement Input, Loss Severity [Member]
Available For Sale Securities [Abstract]
Debt Securities, Available-for-sale, Measurement Input	0.001	0.001
Fair Value, Measurements, Recurring [Member] | Fair Value Inputs Level 3 [Member] | Minimum [Member] | Puerto Rico government obligations [Member] | Measurement Input, Discount Rate [Member]
Available For Sale Securities [Abstract]
Debt Securities, Available-for-sale, Measurement Input	0.115	0.141
Fair Value, Measurements, Recurring [Member] | Fair Value Inputs Level 3 [Member] | Minimum [Member] | Puerto Rico government obligations [Member] | Measurement Input, Loss Severity [Member]
Available For Sale Securities [Abstract]
Debt Securities, Available-for-sale, Measurement Input	0.239	0.258
Fair Value, Measurements, Recurring [Member] | Fair Value Inputs Level 3 [Member] | Maximum [Member] | Residential MBS [Member] | Private label [Member] | Measurement Input, Discount Rate [Member]
Available For Sale Securities [Abstract]
Debt Securities, Available-for-sale, Measurement Input	0.166	0.161
Fair Value, Measurements, Recurring [Member] | Fair Value Inputs Level 3 [Member] | Maximum [Member] | Residential MBS [Member] | Private label [Member] | Measurement Input, Constant Prepayment Rate [Member]
Available For Sale Securities [Abstract]
Debt Securities, Available-for-sale, Measurement Input	0.057	0.069
Fair Value, Measurements, Recurring [Member] | Fair Value Inputs Level 3 [Member] | Maximum [Member] | Residential MBS [Member] | Private label [Member] | Measurement Input, Loss Severity [Member]
Available For Sale Securities [Abstract]
Debt Securities, Available-for-sale, Measurement Input	0.101	0.109
Fair Value, Measurements, Recurring [Member] | Fair Value Inputs Level 3 [Member] | Maximum [Member] | Puerto Rico government obligations [Member] | Measurement Input, Discount Rate [Member]
Available For Sale Securities [Abstract]
Debt Securities, Available-for-sale, Measurement Input	0.115	0.141
Fair Value, Measurements, Recurring [Member] | Fair Value Inputs Level 3 [Member] | Maximum [Member] | Puerto Rico government obligations [Member] | Measurement Input, Loss Severity [Member]
Available For Sale Securities [Abstract]
Debt Securities, Available-for-sale, Measurement Input	0.239	0.258
Fair Value, Measurements, Recurring [Member] | Fair Value Inputs Level 3 [Member] | Weighted Average [Member] | Residential MBS [Member] | Private label [Member] | Measurement Input, Discount Rate [Member]
Available For Sale Securities [Abstract]
Debt Securities, Available-for-sale, Measurement Input	0.166	0.161
Fair Value, Measurements, Recurring [Member] | Fair Value Inputs Level 3 [Member] | Weighted Average [Member] | Residential MBS [Member] | Private label [Member] | Measurement Input, Constant Prepayment Rate [Member]
Available For Sale Securities [Abstract]
Debt Securities, Available-for-sale, Measurement Input	0.032	0.037
Fair Value, Measurements, Recurring [Member] | Fair Value Inputs Level 3 [Member] | Weighted Average [Member] | Residential MBS [Member] | Private label [Member] | Measurement Input, Loss Severity [Member]
Available For Sale Securities [Abstract]
Debt Securities, Available-for-sale, Measurement Input	0.049	0.042
Fair Value, Measurements, Recurring [Member] | Fair Value Inputs Level 3 [Member] | Weighted Average [Member] | Puerto Rico government obligations [Member] | Measurement Input, Discount Rate [Member]
Available For Sale Securities [Abstract]
Debt Securities, Available-for-sale, Measurement Input	0.115	0.141
Fair Value, Measurements, Recurring [Member] | Fair Value Inputs Level 3 [Member] | Weighted Average [Member] | Puerto Rico government obligations [Member] | Measurement Input, Loss Severity [Member]
Available For Sale Securities [Abstract]
Debt Securities, Available-for-sale, Measurement Input	0.239	0.258