DEBT SECURITIES - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022	Dec. 31, 2022	Dec. 31, 2021
Schedule Of Investments [Line Items]
Fair value	$ 5,589,256		$ 5,599,520
Gross Unrealized Losses	711,278		798,466
Available-for-sale, allowance for credit losses	449		458
Allowance for credit losses, Held-to-Maturity securities	7,646		8,286
Debt Securities, Held-to-maturity	431,395		437,537
Interest Receivable	63,841		69,730
Municipal Bonds [Member] | Puerto Rico [Member]
Schedule Of Investments [Line Items]
Allowance for credit losses, Held-to-Maturity securities	7,646	$ 12,324	8,286	$ 8,571
Provision for credit loss expense	(640)	3,753
Debt Securities, Held-to-maturity	165,800		165,710
Puerto Rico government obligations [Member]
Schedule Of Investments [Line Items]
Available-for-sale, allowance for credit losses	400		400
Residential Mortgage Backed Securities [Member]
Schedule Of Investments [Line Items]
Fair value	2,896,655		2,941,458
Gross Unrealized Losses	467,427		514,499
Available-for-sale, allowance for credit losses	83		83
Allowance for credit losses, Held-to-Maturity securities	0		0
Debt Securities, Held-to-maturity	161,587		166,739
Residential Mortgage Backed Securities [Member] | Private label [Member]
Schedule Of Investments [Line Items]
Fair value	5,400
Gross Unrealized Losses	2,300
Available-for-sale, allowance for credit losses	100		100
Residential Pass-Through Mortgage Backed Securities Issued By PRHFA [Member]
Schedule Of Investments [Line Items]
Fair value	2,200
Gross Unrealized Losses	1,100
Provision For Other Credit Losses No Previous Expected Credit Losses	400
Available-for-sale Securities [Member]
Schedule Of Investments [Line Items]
Available-for-sale, allowance for credit losses	449	711	458	1,105
Provision For Other Credit Losses Previous Expected Credit Losses	9	388
Charge-offs		6
Available-for-sale Securities [Member] | Puerto Rico government obligations [Member]
Schedule Of Investments [Line Items]
Available-for-sale, allowance for credit losses	366	308	375	308
Provision For Other Credit Losses Previous Expected Credit Losses	9	0
Charge-offs		0
Available-for-sale Securities [Member] | Residential Mortgage Backed Securities [Member] | Private label [Member]
Schedule Of Investments [Line Items]
Available-for-sale, allowance for credit losses	83	403	$ 83	$ 797
Provision For Other Credit Losses Previous Expected Credit Losses	$ 0	388
Charge-offs		$ 6
Available-for-sale Securities [Member] | Residential Mortgage Backed Securities [Member] | Private label [Member] | FICO Score, Greater than 700 [Member] | LTV Less than 80 Percent [Member]
Schedule Of Investments [Line Items]
Financing Receivable, Credit Quality, Additional Information	The underlying collateral is fixed-rate, single-family residential mortgage loans in the United States with original FICO scores over 700 and moderate loan-to-value ratios (under 80%), as well as moderate delinquency levels.
Available-for-sale Securities [Member] | Residential Mortgage Backed Securities [Member] | Private label [Member] | London Interbank Offered Rate (LIBOR) [Member]
Schedule Of Investments [Line Items]
Loans Receivable, Description of Variable Rate Basis	The interest rate on these private-label MBS is variable, tied to 3-month LIBOR, and limited to the weighted-average coupon on the underlying collateral.