FAIR VLUE - Assets and Liabilites Measured at Fair Value on Recurring Basis Using Unobservable Inputs (Level 3) (Detail) $ in Thousands	Jun. 30, 2020 USD ($)	Dec. 31, 2019 USD ($)
Debt Securities, Available-for-sale, Sale [Abstract]
Debt Securities, Available-for-sale	$ 2,723,171	$ 2,123,525
Puerto Rico Government obligations [Member]
Debt Securities, Available-for-sale, Sale [Abstract]
Debt Securities, Available-for-sale	7,200
Fair Value, Measurements, Recurring [Member] | Fair Value Inputs Level 3 [Member] | Private label [Member] | Valuation Technique, Discounted Cash Flow [Member]
Debt Securities, Available-for-sale, Sale [Abstract]
Debt Securities, Available-for-sale	9,190	11,116
Fair Value, Measurements, Recurring [Member] | Fair Value Inputs Level 3 [Member] | Puerto Rico Government obligations [Member] | Valuation Technique, Discounted Cash Flow [Member]
Debt Securities, Available-for-sale, Sale [Abstract]
Debt Securities, Available-for-sale	$ 2,953	$ 2,974
Fair Value, Measurements, Recurring [Member] | Fair Value Inputs Level 3 [Member] | Minimum [Member] | Private label [Member] | Discount rate [Member]
Debt Securities, Available-for-sale, Sale [Abstract]
Debt Securities, Available-for-sale, Measurement Input	0.125	0.137
Fair Value, Measurements, Recurring [Member] | Fair Value Inputs Level 3 [Member] | Minimum [Member] | Private label [Member] | Prepayment rate [Member]
Debt Securities, Available-for-sale, Sale [Abstract]
Debt Securities, Available-for-sale, Measurement Input	0.068	0.068
Fair Value, Measurements, Recurring [Member] | Fair Value Inputs Level 3 [Member] | Minimum [Member] | Private label [Member] | Projected Cumulative Loss Rate [Member]
Debt Securities, Available-for-sale, Sale [Abstract]
Debt Securities, Available-for-sale, Measurement Input	0.007	0.000
Fair Value, Measurements, Recurring [Member] | Fair Value Inputs Level 3 [Member] | Minimum [Member] | Puerto Rico Government obligations [Member] | Discount rate [Member]
Debt Securities, Available-for-sale, Sale [Abstract]
Debt Securities, Available-for-sale, Measurement Input	0.085	0.069
Fair Value, Measurements, Recurring [Member] | Fair Value Inputs Level 3 [Member] | Minimum [Member] | Puerto Rico Government obligations [Member] | Prepayment rate [Member]
Debt Securities, Available-for-sale, Sale [Abstract]
Debt Securities, Available-for-sale, Measurement Input		0.030
Fair Value, Measurements, Recurring [Member] | Fair Value Inputs Level 3 [Member] | Minimum [Member] | Puerto Rico Government obligations [Member] | Projected Cumulative Loss Rate [Member]
Debt Securities, Available-for-sale, Sale [Abstract]
Debt Securities, Available-for-sale, Measurement Input	0.159
Fair Value, Measurements, Recurring [Member] | Fair Value Inputs Level 3 [Member] | Maximum [Member] | Private label [Member] | Discount rate [Member]
Debt Securities, Available-for-sale, Sale [Abstract]
Debt Securities, Available-for-sale, Measurement Input	0.125	0.137
Fair Value, Measurements, Recurring [Member] | Fair Value Inputs Level 3 [Member] | Maximum [Member] | Private label [Member] | Prepayment rate [Member]
Debt Securities, Available-for-sale, Sale [Abstract]
Debt Securities, Available-for-sale, Measurement Input	0.103	0.103
Fair Value, Measurements, Recurring [Member] | Fair Value Inputs Level 3 [Member] | Maximum [Member] | Private label [Member] | Projected Cumulative Loss Rate [Member]
Debt Securities, Available-for-sale, Sale [Abstract]
Debt Securities, Available-for-sale, Measurement Input	0.233	0.074
Fair Value, Measurements, Recurring [Member] | Fair Value Inputs Level 3 [Member] | Maximum [Member] | Puerto Rico Government obligations [Member] | Discount rate [Member]
Debt Securities, Available-for-sale, Sale [Abstract]
Debt Securities, Available-for-sale, Measurement Input	0.085	0.069
Fair Value, Measurements, Recurring [Member] | Fair Value Inputs Level 3 [Member] | Maximum [Member] | Puerto Rico Government obligations [Member] | Prepayment rate [Member]
Debt Securities, Available-for-sale, Sale [Abstract]
Debt Securities, Available-for-sale, Measurement Input		0.030
Fair Value, Measurements, Recurring [Member] | Fair Value Inputs Level 3 [Member] | Maximum [Member] | Puerto Rico Government obligations [Member] | Projected Cumulative Loss Rate [Member]
Debt Securities, Available-for-sale, Sale [Abstract]
Debt Securities, Available-for-sale, Measurement Input	0.159
Fair Value, Measurements, Recurring [Member] | Fair Value Inputs Level 3 [Member] | Weighted Average [Member] | Private label [Member] | Discount rate [Member]
Debt Securities, Available-for-sale, Sale [Abstract]
Debt Securities, Available-for-sale, Measurement Input	0.125	0.137
Fair Value, Measurements, Recurring [Member] | Fair Value Inputs Level 3 [Member] | Weighted Average [Member] | Private label [Member] | Prepayment rate [Member]
Debt Securities, Available-for-sale, Sale [Abstract]
Debt Securities, Available-for-sale, Measurement Input	0.079	0.079
Fair Value, Measurements, Recurring [Member] | Fair Value Inputs Level 3 [Member] | Weighted Average [Member] | Private label [Member] | Projected Cumulative Loss Rate [Member]
Debt Securities, Available-for-sale, Sale [Abstract]
Debt Securities, Available-for-sale, Measurement Input	0.098	0.028
Fair Value, Measurements, Recurring [Member] | Fair Value Inputs Level 3 [Member] | Weighted Average [Member] | Puerto Rico Government obligations [Member] | Discount rate [Member]
Debt Securities, Available-for-sale, Sale [Abstract]
Debt Securities, Available-for-sale, Measurement Input	0.085	0.069
Fair Value, Measurements, Recurring [Member] | Fair Value Inputs Level 3 [Member] | Weighted Average [Member] | Puerto Rico Government obligations [Member] | Prepayment rate [Member]
Debt Securities, Available-for-sale, Sale [Abstract]
Debt Securities, Available-for-sale, Measurement Input		0.030
Fair Value, Measurements, Recurring [Member] | Fair Value Inputs Level 3 [Member] | Weighted Average [Member] | Puerto Rico Government obligations [Member] | Projected Cumulative Loss Rate [Member]
Debt Securities, Available-for-sale, Sale [Abstract]
Debt Securities, Available-for-sale, Measurement Input	0.159