FAIR VALUE - Assets and Liabilities Measured at Fair Value on Recurring Basis Using Significant Unobservable Inputs (Level 3) (Detail) $ in Thousands	Sep. 30, 2023 USD ($)	Dec. 31, 2022 USD ($)
Available For Sale Securities [Abstract]
Available-For-Sale Securities, Debt Securities	$ 5,175,803	$ 5,599,520
Fair Value, Measurements, Recurring [Member] | Puerto Rico government obligations [Member]
Available For Sale Securities [Abstract]
Available-For-Sale Securities, Debt Securities	1,448	2,201
Fair Value, Measurements, Recurring [Member] | Fair Value Inputs Level 3 [Member] | Private label [Member] | Valuation Technique, Discounted Cash Flow [Member] | Residential Portfolio Segment [Member]
Available For Sale Securities [Abstract]
Available-For-Sale Securities, Debt Securities	4,918	5,794
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	1,448	2,201
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	$ 1,448	$ 2,201
Fair Value, Measurements, Recurring [Member] | Fair Value Inputs Level 3 [Member] | Minimum [Member] | Private label [Member] | Measurement Input, Discount Rate [Member] | Residential Portfolio Segment [Member]
Available For Sale Securities [Abstract]
Debt Securities, Available-for-sale, Measurement Input	0.173	0.162
Fair Value, Measurements, Recurring [Member] | Fair Value Inputs Level 3 [Member] | Minimum [Member] | Private label [Member] | Measurement Input, Constant Prepayment Rate [Member] | Residential Portfolio Segment [Member]
Available For Sale Securities [Abstract]
Debt Securities, Available-for-sale, Measurement Input	0.012	0.015
Fair Value, Measurements, Recurring [Member] | Fair Value Inputs Level 3 [Member] | Minimum [Member] | Private label [Member] | Measurement Input, Loss Severity [Member] | Residential Portfolio Segment [Member]
Available For Sale Securities [Abstract]
Debt Securities, Available-for-sale, Measurement Input	0.002	0.003
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	0.139	0.129
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	0.245	0.193
Fair Value, Measurements, Recurring [Member] | Fair Value Inputs Level 3 [Member] | Maximum [Member] | Private label [Member] | Measurement Input, Discount Rate [Member] | Residential Portfolio Segment [Member]
Available For Sale Securities [Abstract]
Debt Securities, Available-for-sale, Measurement Input	0.173	0.162
Fair Value, Measurements, Recurring [Member] | Fair Value Inputs Level 3 [Member] | Maximum [Member] | Private label [Member] | Measurement Input, Constant Prepayment Rate [Member] | Residential Portfolio Segment [Member]
Available For Sale Securities [Abstract]
Debt Securities, Available-for-sale, Measurement Input	0.088	0.152
Fair Value, Measurements, Recurring [Member] | Fair Value Inputs Level 3 [Member] | Maximum [Member] | Private label [Member] | Measurement Input, Loss Severity [Member] | Residential Portfolio Segment [Member]
Available For Sale Securities [Abstract]
Debt Securities, Available-for-sale, Measurement Input	0.137	0.156
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	0.139	0.129
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	0.245	0.193
Fair Value, Measurements, Recurring [Member] | Fair Value Inputs Level 3 [Member] | Weighted Average [Member] | Private label [Member] | Measurement Input, Discount Rate [Member] | Residential Portfolio Segment [Member]
Available For Sale Securities [Abstract]
Debt Securities, Available-for-sale, Measurement Input	0.173	0.162
Fair Value, Measurements, Recurring [Member] | Fair Value Inputs Level 3 [Member] | Weighted Average [Member] | Private label [Member] | Measurement Input, Constant Prepayment Rate [Member] | Residential Portfolio Segment [Member]
Available For Sale Securities [Abstract]
Debt Securities, Available-for-sale, Measurement Input	0.053	0.118
Fair Value, Measurements, Recurring [Member] | Fair Value Inputs Level 3 [Member] | Weighted Average [Member] | Private label [Member] | Measurement Input, Loss Severity [Member] | Residential Portfolio Segment [Member]
Available For Sale Securities [Abstract]
Debt Securities, Available-for-sale, Measurement Input	0.055	0.056
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	0.139	0.129
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	0.245	0.193