FAIR VALUE - Assets and Liabilities Measured at Fair Value on Recurring Basis Using Significant Unobservable Inputs (Level 3) (Details) $ in Thousands	Mar. 31, 2026 USD ($)	Dec. 31, 2025 USD ($)
Available For Sale Securities [Abstract]
Available-For-Sale Securities, Debt Securities	$ 4,668,697	$ 4,554,032
Residential MBS [Member]
Available For Sale Securities [Abstract]
Available-For-Sale Securities, Debt Securities	3,131,706	2,948,895
Residential MBS [Member] \| Private label [Member]
Available For Sale Securities [Abstract]
Available-For-Sale Securities, Debt Securities	3,113	3,266
Fair Value, Measurements, Recurring [Member] \| Puerto Rico government obligations [Member]
Available For Sale Securities [Abstract]
Available-For-Sale Securities, Debt Securities	1,609	1,620
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	3,113	3,266
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	1,609	1,620
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	$ 1,609	$ 1,620
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	0.162	0.159
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	0.016	0.016
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	0.108	0.108
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	0.236	0.240
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	0.162	0.159
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	0.080	0.080
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	0.125	0.114
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	0.108	0.108
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	0.236	0.240
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	0.162	0.159
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	0.025	0.031
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	0.068	0.055
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	0.108	0.108
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	0.236	0.240

Fair Value, Measurements, Recurring [Member] | Fair Value Inputs Level 3 [Member] | Residential MBS [Member] | Private label [Member] | Valuation Technique, Discounted Cash Flow [Member]

Fair Value, Measurements, Recurring [Member] | Fair Value Inputs Level 3 [Member] | Puerto Rico government obligations [Member]

Fair Value, Measurements, Recurring [Member] | Fair Value Inputs Level 3 [Member] | Puerto Rico government obligations [Member] | Valuation Technique, Discounted Cash Flow [Member]

Fair Value, Measurements, Recurring [Member] | Fair Value Inputs Level 3 [Member] | Minimum [Member] | Puerto Rico government obligations [Member] | Measurement Input, Discount Rate [Member]

Fair Value, Measurements, Recurring [Member] | Fair Value Inputs Level 3 [Member] | Minimum [Member] | Puerto Rico government obligations [Member] | Measurement Input, Loss Severity [Member]

Fair Value, Measurements, Recurring [Member] | Fair Value Inputs Level 3 [Member] | Maximum [Member] | Puerto Rico government obligations [Member] | Measurement Input, Discount Rate [Member]

Fair Value, Measurements, Recurring [Member] | Fair Value Inputs Level 3 [Member] | Maximum [Member] | Puerto Rico government obligations [Member] | Measurement Input, Loss Severity [Member]

Fair Value, Measurements, Recurring [Member] | Fair Value Inputs Level 3 [Member] | Weighted Average [Member] | Puerto Rico government obligations [Member] | Measurement Input, Discount Rate [Member]

Fair Value, Measurements, Recurring [Member] | Fair Value Inputs Level 3 [Member] | Weighted Average [Member] | Puerto Rico government obligations [Member] | Measurement Input, Loss Severity [Member]