INVESTMENT SECURITIES - Additional Information (Detail) - USD ($)	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021	Dec. 31, 2021	Dec. 31, 2020
Schedule Of Investments [Line Items]
Fair value	$ 6,424,660,000		$ 6,453,761,000
Gross unrealized loss	417,829,000		108,537,000
Available-for-sale, allowance for credit losses	711,000	$ 1,183,000	1,105,000	$ 1,310,000
Charge-offs	6,000
Allowance for credit losses, Held-to-Maturity securities	$ 12,324,000		8,571,000
Debt Securities, Held-to-maturity, Threshold Period Past Due	30 days
Interest Receivable	$ 57,425,000		61,507,000
Past Due [Member]
Schedule Of Investments [Line Items]
Debt Securities, Held-to-maturity	0		0
Municipal Bonds [Member] | Puerto Rico [Member]
Schedule Of Investments [Line Items]
Allowance for credit losses, Held-to-Maturity securities	12,324,000	8,869,000	8,571,000	8,845,000
Provision for credit loss expense	3,753,000	24,000
Debt Securities, Held-to-maturity	178,059,000		178,133,000
Debt Securities Held To Maturity Allowance For Credit Loss Period Increase Decrease	3,700,000
Municipal Bonds [Member] | Puerto Rico [Member] | Pass [Member]
Schedule Of Investments [Line Items]
Debt Securities, Held-to-maturity	178,059,000		178,133,000
Puerto Rico government obligations [Member]
Schedule Of Investments [Line Items]
Available-for-sale, allowance for credit losses	308,000	308,000	308,000	308,000
Charge-offs	0
Puerto Rico government obligations [Member] | Residential Mortgage Backed Securities [Member]
Schedule Of Investments [Line Items]
Fair value	2,700,000
Gross unrealized loss	800,000
Provision for credit loss expense	300,000
MBS [Member]
Schedule Of Investments [Line Items]
Fair value	3,823,983,000		4,044,443,000
Gross unrealized loss	269,415,000		66,477,000
Available-for-sale, allowance for credit losses	403,000		797,000
MBS [Member] | Private label [Member]
Schedule Of Investments [Line Items]
Fair value	6,900,000
Gross unrealized loss	2,600,000
Available-for-sale, allowance for credit losses	403,000	$ 875,000	797,000	$ 1,002,000
Charge-offs	$ 6,000
Available-for-sale Securities [Member]
Schedule Of Investments [Line Items]
Percentage Of Debt Securities Government And Government Sponsored Agencies	99.00%
Interest Receivable	$ 11,100,000		10,100,000
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 are 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	$ 1,700,000		$ 3,400,000