DEBT SECURITIES - Investment Securities Available for Sale (Detail) - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023	Mar. 31, 2023	Dec. 31, 2022
Schedule Of Available For Sale Securities [Line Items]
Amortized cost	$ 5,695,485	$ 5,863,294
Gross Unrealized Gains	273	250
Gross Unrealized Losses	648,137	633,049
Allowance for Credit Losses	442	511	$ 449	$ 458
Fair value	$ 5,047,179	$ 5,229,984
Weighted-average yield	1.25%	1.24%
Interest receivable	$ 73,154	$ 77,716
Available-for-sale Securities [Member]
Schedule Of Available For Sale Securities [Line Items]
Interest receivable	10,200	10,600
Federal Home Loan Bank Borrowings [Member] | Asset Pledged as Collateral [Member]
Schedule Of Available For Sale Securities [Line Items]
Amortized cost	552,300	527,200
Fair value	473,000	477,900
U.S. Treasury securities [Member]
Schedule Of Available For Sale Securities [Line Items]
Amortized cost Due within one year	100,519	80,314
Gross Unrealized Gains Due within one year	0	0
Gross Unrealized Losses Due within one year	3,144	2,144
Allowance for Credit Losses within one year	0	0
Fair value Due within one year	$ 97,375	$ 78,170
Weighted-average yield Due within one year	0.70%	0.66%
Amortized cost After 1 to 5 years	$ 19,881	$ 60,239
Gross Unrealized Gains After 1 to 5 years	0	0
Gross Unrealized Losses After 1 to 5 years	1,188	3,016
Allowance for Credit Losses After 1 to 5 years	0	0
Fair value After 1 to 5 years	$ 18,693	$ 57,223
Weighted-average yield After 1 to 5 years	0.65%	0.75%
U.S. GSE's obligations [Member]
Schedule Of Available For Sale Securities [Line Items]
Amortized cost Due within one year	$ 683,768	$ 542,847
Gross Unrealized Gains Due within one year	0	0
Gross Unrealized Losses Due within one year	17,920	15,832
Allowance for Credit Losses within one year	0	0
Fair value Due within one year	$ 665,848	$ 527,015
Weighted-average yield Due within one year	0.90%	0.77%
Amortized cost After 1 to 5 years	$ 1,698,700	$ 1,899,620
Gross Unrealized Gains After 1 to 5 years	59	49
Gross Unrealized Losses After 1 to 5 years	128,048	135,347
Allowance for Credit Losses After 1 to 5 years	0	0
Fair value After 1 to 5 years	$ 1,570,711	$ 1,764,322
Weighted-average yield After 1 to 5 years	0.82%	0.86%
Amortized cost After 5 to 10 years	$ 8,850	$ 8,850
Gross Unrealized Gains After 5 to 10 years	0	0
Gross Unrealized Losses After 5 to 10 years	754	687
Allowance for Credit Losses After 5 to 10 years	0	0
Fair value After 5 to 10 years	$ 8,096	$ 8,163
Weighted-average yield After 5 to 10 years	2.64%	2.64%
Amortized cost After 10 years	$ 8,762	$ 8,891
Gross Unrealized Gains After 10 years	3	8
Gross Unrealized Losses After 10 years	4	2
Allowance for Credit Losses After 10 years	0	0
Fair value After 10 years	$ 8,761	$ 8,897
Weighted-average yield After 10 years	5.51%	5.49%
Puerto Rico government obligations [Member]
Schedule Of Available For Sale Securities [Line Items]
Amortized cost After 10 years	$ 3,112	$ 3,156
Gross Unrealized Gains After 10 years	0	0
Gross Unrealized Losses After 10 years	1,235	1,346
Allowance for Credit Losses After 10 years	326	395
Fair value After 10 years	$ 1,551	$ 1,415
Weighted-average yield After 10 years	0.00%	0.00%
Allowance for Credit Losses	$ 326	$ 395	$ 366	$ 375
United States And Puerto Rico Government Obligations [Member]
Schedule Of Available For Sale Securities [Line Items]
Amortized cost	2,523,592	2,603,917
Gross Unrealized Gains	62	57
Gross Unrealized Losses	152,293	158,374
Allowance for Credit Losses	326	395
Fair value	$ 2,371,035	$ 2,445,205
Weighted-average yield	0.86%	0.85%
Residential MBS [Member]
Schedule Of Available For Sale Securities [Line Items]
Amortized cost	$ 2,983,034	$ 3,069,139
Gross Unrealized Gains	209	193
Gross Unrealized Losses	456,073	436,055
Allowance for Credit Losses	116	116
Fair value	$ 2,527,054	$ 2,633,161
Weighted-average yield	1.55%	1.55%
Residential MBS [Member] | FHLMC [Member]
Schedule Of Available For Sale Securities [Line Items]
Amortized cost Due within one year	$ 7
Gross Unrealized Gains Due within one year	0
Gross Unrealized Losses Due within one year	0
Allowance for Credit Losses within one year	0
Fair value Due within one year	$ 7
Weighted-average yield Due within one year	4.50%
Amortized cost After 1 to 5 years	$ 17,827	$ 19,561
Gross Unrealized Gains After 1 to 5 years	0	0
Gross Unrealized Losses After 1 to 5 years	856	868
Allowance for Credit Losses After 1 to 5 years	0	0
Fair value After 1 to 5 years	$ 16,971	$ 18,693
Weighted-average yield After 1 to 5 years	2.06%	2.06%
Amortized cost After 5 to 10 years	$ 146,335	$ 153,308
Gross Unrealized Gains After 5 to 10 years	0	0
Gross Unrealized Losses After 5 to 10 years	13,488	12,721
Allowance for Credit Losses After 5 to 10 years	0	0
Fair value After 5 to 10 years	$ 132,847	$ 140,587
Weighted-average yield After 5 to 10 years	1.55%	1.55%
Amortized cost After 10 years	$ 970,917	$ 991,060
Gross Unrealized Gains After 10 years	8	15
Gross Unrealized Losses After 10 years	169,069	161,197
Allowance for Credit Losses After 10 years	0	0
Fair value After 10 years	$ 801,856	$ 829,878
Weighted-average yield After 10 years	1.41%	1.41%
Amortized cost	$ 1,135,086	$ 1,163,929
Gross Unrealized Gains	8	15
Gross Unrealized Losses	183,413	174,786
Allowance for Credit Losses	0	0
Fair value	$ 951,681	$ 989,158
Weighted-average yield	1.44%	1.44%
Residential MBS [Member] | GNMA [Member]
Schedule Of Available For Sale Securities [Line Items]
Amortized cost Due within one year	$ 281	$ 254
Gross Unrealized Gains Due within one year	0	0
Gross Unrealized Losses Due within one year	3	3
Allowance for Credit Losses within one year	0	0
Fair value Due within one year	$ 278	$ 251
Weighted-average yield Due within one year	3.25%	3.27%
Amortized cost After 1 to 5 years	$ 14,493	$ 16,882
Gross Unrealized Gains After 1 to 5 years	0	0
Gross Unrealized Losses After 1 to 5 years	789	872
Allowance for Credit Losses After 1 to 5 years	0	0
Fair value After 1 to 5 years	$ 13,704	$ 16,010
Weighted-average yield After 1 to 5 years	1.11%	1.19%
Amortized cost After 5 to 10 years	$ 26,563	$ 27,916
Gross Unrealized Gains After 5 to 10 years	4	8
Gross Unrealized Losses After 5 to 10 years	2,387	2,247
Allowance for Credit Losses After 5 to 10 years	0	0
Fair value After 5 to 10 years	$ 24,180	$ 25,677
Weighted-average yield After 5 to 10 years	1.65%	1.62%
Amortized cost After 10 years	$ 201,129	$ 206,254
Gross Unrealized Gains After 10 years	165	87
Gross Unrealized Losses After 10 years	25,748	22,786
Allowance for Credit Losses After 10 years	0	0
Fair value After 10 years	$ 175,546	$ 183,555
Weighted-average yield After 10 years	2.60%	2.57%
Amortized cost	$ 242,466	$ 251,306
Gross Unrealized Gains	169	95
Gross Unrealized Losses	28,927	25,908
Allowance for Credit Losses	0	0
Fair value	$ 213,708	$ 225,493
Weighted-average yield	2.41%	2.38%
Residential MBS [Member] | FNMA [Member]
Schedule Of Available For Sale Securities [Line Items]
Amortized cost After 1 to 5 years	$ 29,694	$ 32,489
Gross Unrealized Gains After 1 to 5 years	0	0
Gross Unrealized Losses After 1 to 5 years	1,411	1,423
Allowance for Credit Losses After 1 to 5 years	0	0
Fair value After 1 to 5 years	$ 28,283	$ 31,066
Weighted-average yield After 1 to 5 years	2.11%	2.11%
Amortized cost After 5 to 10 years	$ 284,547	$ 293,492
Gross Unrealized Gains After 5 to 10 years	0	0
Gross Unrealized Losses After 5 to 10 years	24,926	23,146
Allowance for Credit Losses After 5 to 10 years	0	0
Fair value After 5 to 10 years	$ 259,621	$ 270,346
Weighted-average yield After 5 to 10 years	1.73%	1.70%
Amortized cost After 10 years	$ 1,016,944	$ 1,047,298
Gross Unrealized Gains After 10 years	32	83
Gross Unrealized Losses After 10 years	161,363	156,344
Allowance for Credit Losses After 10 years	0	0
Fair value After 10 years	$ 855,613	$ 891,037
Weighted-average yield After 10 years	1.36%	1.37%
Amortized cost	$ 1,331,185	$ 1,373,279
Gross Unrealized Gains	32	83
Gross Unrealized Losses	187,700	180,913
Allowance for Credit Losses	0	0
Fair value	$ 1,143,517	$ 1,192,449
Weighted-average yield	1.46%	1.46%
Residential MBS [Member] | Collateralized mortgage obligations ("CMOs") issued or guaranteed by FHLMC, FNMA and GNMA [Member]
Schedule Of Available For Sale Securities [Line Items]
Amortized cost After 10 years	$ 267,401	$ 273,539
Gross Unrealized Gains After 10 years	0	0
Gross Unrealized Losses After 10 years	53,977	52,263
Allowance for Credit Losses After 10 years	0	0
Fair value After 10 years	$ 213,424	$ 221,276
Weighted-average yield After 10 years	1.54%	1.54%
Residential MBS [Member] | Private label [Member]
Schedule Of Available For Sale Securities [Line Items]
Amortized cost After 5 to 10 years	$ 400
Gross Unrealized Gains After 5 to 10 years	0
Gross Unrealized Losses After 5 to 10 years	93
Allowance for Credit Losses After 5 to 10 years	2
Fair value After 5 to 10 years	$ 305
Weighted-average yield After 5 to 10 years	8.44%
Amortized cost After 10 years	$ 6,496	$ 7,086
Gross Unrealized Gains After 10 years	0	0
Gross Unrealized Losses After 10 years	1,963	2,185
Allowance for Credit Losses After 10 years	114	116
Fair value After 10 years	$ 4,419	$ 4,785
Weighted-average yield After 10 years	7.58%	7.66%
Allowance for Credit Losses	$ 100	$ 100
Weighted-average yield	7.63%
Commercial Mortgage Backed Securities [Member]
Schedule Of Available For Sale Securities [Line Items]
Amortized cost After 1 to 5 years	$ 44,443	45,022
Gross Unrealized Gains After 1 to 5 years	2	0
Gross Unrealized Losses After 1 to 5 years	7,044	6,898
Allowance for Credit Losses After 1 to 5 years	0	0
Fair value After 1 to 5 years	$ 37,401	$ 38,124
Weighted-average yield After 1 to 5 years	2.18%	2.17%
Amortized cost After 5 to 10 years	$ 22,252	$ 22,386
Gross Unrealized Gains After 5 to 10 years	0	0
Gross Unrealized Losses After 5 to 10 years	2,785	2,685
Allowance for Credit Losses After 5 to 10 years	0	0
Fair value After 5 to 10 years	$ 19,467	$ 19,701
Weighted-average yield After 5 to 10 years	2.16%	2.16%
Amortized cost After 10 years	$ 122,164	$ 122,830
Gross Unrealized Gains After 10 years	0	0
Gross Unrealized Losses After 10 years	29,942	29,037
Allowance for Credit Losses After 10 years	0	0
Fair value After 10 years	$ 92,222	$ 93,793
Weighted-average yield After 10 years	1.36%	1.36%
Amortized cost	$ 188,859	$ 190,238
Gross Unrealized Gains	2	0
Gross Unrealized Losses	39,771	38,620
Allowance for Credit Losses	0	0
Fair value	$ 149,090	$ 151,618
Weighted-average yield	1.64%	1.64%
Mortgage Backed Securities [Member]
Schedule Of Available For Sale Securities [Line Items]
Amortized cost	$ 3,171,893	$ 3,259,377
Gross Unrealized Gains	211	193
Gross Unrealized Losses	495,844	474,675
Allowance for Credit Losses	116	116
Fair value	$ 2,676,144	$ 2,784,779
Weighted-average yield	1.55%	1.55%
Unisured Portion Of Government Deposits [Member] | Asset Pledged as Collateral [Member]
Schedule Of Available For Sale Securities [Line Items]
Amortized cost	$ 3,100,000	$ 3,200,000
Fair value	$ 2,800,000	$ 2,800,000