DEBT SECURITIES - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022	Jun. 30, 2023	Dec. 31, 2022	Jun. 30, 2022	Dec. 31, 2021
Schedule Of Investments [Line Items]
Fair value	$ 5,175,803		$ 5,175,803			$ 5,599,520
Gross Unrealized Losses	844,877		844,877			798,466
Available-for-sale, allowance for credit losses	465	$ 664	465	$ 664	$ 433	458	$ 676	$ 1,105
Provision For Other Credit Losses Previous Expected Credit Losses	(32)	12	(7)	435
Charge-offs			0	(6)
Allowance for credit losses, Held-to-Maturity securities	2,250		2,250			8,286
Provision for credit loss expense	(6,119)	(640)	(6,029)	(749)
Debt Securities, Held-to-maturity	359,169		359,169			437,537
Accrued interest receivable	$ 68,783		$ 68,783			69,730
FICO Score, Greater than 700 [Member] | LTV Less than 80 Percent [Member] | Private label [Member]
Schedule Of Investments [Line Items]
Loan To Value Coverage Percentage	80.00%		80.00%
Municipal Bonds [Member]
Schedule Of Investments [Line Items]
Allowance for credit losses, Held-to-Maturity securities	$ 2,250	8,257	$ 2,250	8,257		8,286		8,571
Debt Securities, Held-to-maturity, Reduction, Amount Refinanced	46,500
Puerto Rico government obligations [Member]
Schedule Of Investments [Line Items]
Available-for-sale, allowance for credit losses	382	374	382	374	350	375	386	308
Provision For Other Credit Losses Previous Expected Credit Losses	(32)	12	(7)	(66)
Charge-offs			0	0
Residential MBS [Member]
Schedule Of Investments [Line Items]
Fair value	2,580,395		2,580,395			2,941,458
Gross Unrealized Losses	578,884		578,884			514,499
Available-for-sale, allowance for credit losses	83		83			83
Allowance for credit losses, Held-to-Maturity securities	0		0			0
Debt Securities, Held-to-maturity	150,650		150,650			166,739
Residential MBS [Member] | Private label [Member]
Schedule Of Investments [Line Items]
Available-for-sale, allowance for credit losses	100		$ 100			100
Residential MBS [Member] | SOFR [Member] | Private label [Member]
Schedule Of Investments [Line Items]
Spread on variable rate			0.26161%
Debt Instrument Description Of Variable Rate Basis			3-month CME Term SOFR
Residential MBS [Member] | Private label [Member]
Schedule Of Investments [Line Items]
Available-for-sale, allowance for credit losses	83	290	$ 83	290	$ 83	83	$ 290	$ 797
Provision For Other Credit Losses Previous Expected Credit Losses	0	$ 0	0	501
Charge-offs			0	$ (6)
Available-for-sale Securities [Member]
Schedule Of Investments [Line Items]
Accrued interest receivable	10,800		10,800			11,100
Held-to-maturity Securities [Member]
Schedule Of Investments [Line Items]
Accrued interest receivable	$ 2,800		$ 2,800			$ 5,500