DEBT SECURITIES - Additional Information (Detail) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021	Mar. 31, 2022	Dec. 31, 2021	Mar. 31, 2021	Dec. 31, 2020
Schedule Of Investments [Line Items]
Fair value	$ 6,081,120,000		$ 6,081,120,000			$ 6,453,761,000
Gross Unrealized Loss	590,132,000		590,132,000			108,537,000
Available-for-sale, allowance for credit losses	676,000		676,000			1,105,000
Allowance for credit losses, Held-to-Maturity securities	8,885,000		8,885,000			8,571,000
Debt Securities, Held-to-maturity	$ 458,227,000		$ 458,227,000
Debt Securities, Held-to-maturity, Threshold Period Past Due	30 days		30 days
Interest Receivable	$ 62,501,000		$ 62,501,000			61,507,000
Securities Held To Maturity, Purchased	280,200,000
Past Due [Member]
Schedule Of Investments [Line Items]
Debt Securities, Held-to-maturity	0		0			0
Municipal Bonds [Member] | Puerto Rico [Member]
Schedule Of Investments [Line Items]
Available-for-sale, allowance for credit losses	8,900,000		8,900,000			8,600,000
Allowance for credit losses, Held-to-Maturity securities	8,885,000	$ 10,685,000	8,885,000	$ 10,685,000	$ 12,324,000	8,571,000	$ 8,869,000	$ 8,845,000
Debt Securities, Held-to-maturity	178,415,000		178,415,000			178,133,000
Debt Securities Held To Maturity Allowance For Credit Loss Period Increase Decrease			300,000
Puerto Rico government obligations [Member] | Residential Mortgage Backed Securities [Member]
Schedule Of Investments [Line Items]
Fair value	2,800,000		2,800,000
Gross Unrealized Loss	600,000		600,000
Available-for-sale, allowance for credit losses	400,000		400,000
MBS [Member]
Schedule Of Investments [Line Items]
Fair value	3,517,827,000		3,517,827,000			4,044,443,000
Gross Unrealized Loss	405,283,000		405,283,000			66,477,000
Available-for-sale, allowance for credit losses	290,000		290,000			797,000
Allowance for credit losses, Held-to-Maturity securities	0		0
Debt Securities, Held-to-maturity	279,812,000		279,812,000
MBS [Member] | Private label [Member]
Schedule Of Investments [Line Items]
Fair value	6,400,000		6,400,000
Gross Unrealized Loss	2,800,000		2,800,000
Available-for-sale, allowance for credit losses	300,000		300,000			800,000
Available-for-sale Securities [Member]
Schedule Of Investments [Line Items]
Available-for-sale, allowance for credit losses	676,000	1,166,000	676,000	1,166,000	711,000	1,105,000	1,183,000	1,310,000
Charge-offs		17,000	6,000	17,000
Interest Receivable	11,200,000		11,200,000			10,100,000
Available-for-sale Securities [Member] | Puerto Rico government obligations [Member]
Schedule Of Investments [Line Items]
Available-for-sale, allowance for credit losses	386,000	308,000	386,000	308,000	308,000	308,000	308,000	308,000
Charge-offs		0	0	0
Available-for-sale Securities [Member] | MBS [Member] | Private label [Member]
Schedule Of Investments [Line Items]
Available-for-sale, allowance for credit losses	290,000	858,000	290,000	858,000	$ 403,000	797,000	$ 875,000	$ 1,002,000
Charge-offs		17,000	$ 6,000	17,000
Available-for-sale Securities [Member] | MBS [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] | MBS [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.
Held-to-maturity Securities [Member]
Schedule Of Investments [Line Items]
Interest Receivable	4,200,000		$ 4,200,000			$ 3,400,000
Held-to-maturity Securities [Member] | Municipal Bonds [Member] | Puerto Rico [Member]
Schedule Of Investments [Line Items]
Provision for credit loss expense	$ (3,439,000)	$ 1,816,000	$ 314,000	$ 1,840,000