DEBT SECURITIES - Available-for-Sale Investments Classified by Contractual Maturity Date (Details) - USD ($) $ in Thousands	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Schedule Of Available For Sale Securities [Line Items]
Amortized cost	$ 5,125,408	$ 5,863,294
Gross Unrealized Gains	183	250
Gross Unrealized Losses	559,768	633,049
Allowance for Credit Losses	521	511
Fair value	$ 4,565,302	$ 5,229,984
Weighted-average yield	1.45%	1.24%
Interest receivable	$ 71,881	$ 77,716
Available-for-Sale Securities [Member]
Schedule Of Available For Sale Securities [Line Items]
Allowance for Credit Losses	521	511	$ 458	$ 1,105
Interest receivable	9,600	10,600
Federal Home Loan Bank Borrowings [Member] | Asset Pledged as Collateral [Member]
Schedule Of Available For Sale Securities [Line Items]
Amortized cost	533,700	527,200
Fair value	466,100	477,900
U.S. Treasury securities [Member]
Schedule Of Available For Sale Securities [Line Items]
Amortized cost Due within one year	59,992	80,314
Gross Unrealized Gains Due within one year	0	0
Gross Unrealized Losses Due within one year	803	2,144
Allowance for Credit Losses within one year	0	0
Fair value Due within one year	$ 59,189	$ 78,170
Weighted-average yield Due within one year	0.75%	0.66%
Amortized cost After 1 to 5 years		$ 60,239
Gross Unrealized Gains After 1 to 5 years		0
Gross Unrealized Losses After 1 to 5 years		3,016
Allowance for Credit Losses After 1 to 5 years		0
Fair value After 1 to 5 years		$ 57,223
Weighted-average yield After 1 to 5 years		0.75%
U.S. GSE's obligations [Member]
Schedule Of Available For Sale Securities [Line Items]
Amortized cost Due within one year	$ 1,090,678	$ 542,847
Gross Unrealized Gains Due within one year	0	0
Gross Unrealized Losses Due within one year	22,826	15,832
Allowance for Credit Losses within one year	0	0
Fair value Due within one year	$ 1,067,852	$ 527,015
Weighted-average yield Due within one year	0.79%	0.77%
Amortized cost After 1 to 5 years	$ 817,835	$ 1,899,620
Gross Unrealized Gains After 1 to 5 years	39	49
Gross Unrealized Losses After 1 to 5 years	53,195	135,347
Allowance for Credit Losses After 1 to 5 years	0	0
Fair value After 1 to 5 years	$ 764,679	$ 1,764,322
Weighted-average yield After 1 to 5 years	0.96%	0.86%
Amortized cost After 5 to 10 years		$ 8,850
Gross Unrealized Gains After 5 to 10 years		0
Gross Unrealized Losses After 5 to 10 years		687
Allowance for Credit Losses After 5 to 10 years		0
Fair value After 5 to 10 years		$ 8,163
Weighted-average yield After 5 to 10 years		2.64%
Amortized cost After 10 years	$ 7,835	$ 8,891
Gross Unrealized Gains After 10 years	0	8
Gross Unrealized Losses After 10 years	35	2
Allowance for Credit Losses After 10 years	0	0
Fair value After 10 years	$ 7,800	$ 8,897
Weighted-average yield After 10 years	4.73%	5.49%
Puerto Rico government obligations [Member]
Schedule Of Available For Sale Securities [Line Items]
Amortized cost After 10 years	$ 2,951	$ 3,156
Gross Unrealized Gains After 10 years	0	0
Gross Unrealized Losses After 10 years	986	1,346
Allowance for Credit Losses After 10 years	345	395
Fair value After 10 years	$ 1,620	$ 1,415
Weighted-average yield After 10 years	0.00%	0.00%
Allowance for Credit Losses	$ 300	$ 400
Puerto Rico government obligations [Member] | Available-for-Sale Securities [Member]
Schedule Of Available For Sale Securities [Line Items]
Allowance for Credit Losses	345	395	375	308
United States And Puerto Rico Government Obligations [Member]
Schedule Of Available For Sale Securities [Line Items]
Amortized cost	1,979,291	2,603,917
Gross Unrealized Gains	39	57
Gross Unrealized Losses	77,845	158,374
Allowance for Credit Losses	345	395
Fair value	$ 1,901,140	$ 2,445,205
Weighted-average yield	0.87%	0.85%
Residential MBS [Member]
Schedule Of Available For Sale Securities [Line Items]
Amortized cost	$ 2,922,124	$ 3,069,139
Gross Unrealized Gains	131	193
Gross Unrealized Losses	440,826	436,055
Allowance for Credit Losses	176	116
Fair value	$ 2,481,253	$ 2,633,161
Weighted-average yield	1.79%	1.55%
Residential MBS [Member] | Freddie Mac (FHLMC) certificates [Member]
Schedule Of Available For Sale Securities [Line Items]
Amortized cost After 1 to 5 years	$ 14,477	$ 19,561
Gross Unrealized Gains After 1 to 5 years	0	0
Gross Unrealized Losses After 1 to 5 years	460	868
Allowance for Credit Losses After 1 to 5 years	0	0
Fair value After 1 to 5 years	$ 14,017	$ 18,693
Weighted-average yield After 1 to 5 years	2.14%	2.06%
Amortized cost After 5 to 10 years	$ 122,548	$ 153,308
Gross Unrealized Gains After 5 to 10 years	0	0
Gross Unrealized Losses After 5 to 10 years	9,977	12,721
Allowance for Credit Losses After 5 to 10 years	0	0
Fair value After 5 to 10 years	$ 112,571	$ 140,587
Weighted-average yield After 5 to 10 years	1.52%	1.55%
Amortized cost After 10 years	$ 936,531	$ 991,060
Gross Unrealized Gains After 10 years	25	15
Gross Unrealized Losses After 10 years	168,691	161,197
Allowance for Credit Losses After 10 years	0	0
Fair value After 10 years	$ 767,865	$ 829,878
Weighted-average yield After 10 years	1.51%	1.41%
Amortized cost	$ 1,073,556	$ 1,163,929
Gross Unrealized Gains	25	15
Gross Unrealized Losses	179,128	174,786
Allowance for Credit Losses	0	0
Fair value	$ 894,453	$ 989,158
Weighted-average yield	1.52%	1.44%
Residential MBS [Member] | Ginnie Mae (GNMA) certificates [Member]
Schedule Of Available For Sale Securities [Line Items]
Amortized cost Due within one year	$ 881	$ 254
Gross Unrealized Gains Due within one year	0	0
Gross Unrealized Losses Due within one year	6	3
Allowance for Credit Losses within one year	0	0
Fair value Due within one year	$ 875	$ 251
Weighted-average yield Due within one year	2.68%	3.27%
Amortized cost After 1 to 5 years	$ 8,025	$ 16,882
Gross Unrealized Gains After 1 to 5 years	0	0
Gross Unrealized Losses After 1 to 5 years	350	872
Allowance for Credit Losses After 1 to 5 years	0	0
Fair value After 1 to 5 years	$ 7,675	$ 16,010
Weighted-average yield After 1 to 5 years	0.71%	1.19%
Amortized cost After 5 to 10 years	$ 67,181	$ 27,916
Gross Unrealized Gains After 5 to 10 years	0	8
Gross Unrealized Losses After 5 to 10 years	6,125	2,247
Allowance for Credit Losses After 5 to 10 years	0	0
Fair value After 5 to 10 years	$ 61,056	$ 25,677
Weighted-average yield After 5 to 10 years	1.86%	1.62%
Amortized cost After 10 years	$ 142,330	$ 206,254
Gross Unrealized Gains After 10 years	16	87
Gross Unrealized Losses After 10 years	22,041	22,786
Allowance for Credit Losses After 10 years	0	0
Fair value After 10 years	$ 120,305	$ 183,555
Weighted-average yield After 10 years	2.78%	2.57%
Amortized cost	$ 218,417	$ 251,306
Gross Unrealized Gains	16	95
Gross Unrealized Losses	28,522	25,908
Allowance for Credit Losses	0	0
Fair value	$ 189,911	$ 225,493
Weighted-average yield	2.42%	2.38%
Residential MBS [Member] | Fannie Mae (FNMA) certificates [Member]
Schedule Of Available For Sale Securities [Line Items]
Amortized cost After 1 to 5 years	$ 21,921	$ 32,489
Gross Unrealized Gains After 1 to 5 years	0	0
Gross Unrealized Losses After 1 to 5 years	689	1,423
Allowance for Credit Losses After 1 to 5 years	0	0
Fair value After 1 to 5 years	$ 21,232	$ 31,066
Weighted-average yield After 1 to 5 years	2.13%	2.11%
Amortized cost After 5 to 10 years	$ 244,966	$ 293,492
Gross Unrealized Gains After 5 to 10 years	0	0
Gross Unrealized Losses After 5 to 10 years	18,874	23,146
Allowance for Credit Losses After 5 to 10 years	0	0
Fair value After 5 to 10 years	$ 226,092	$ 270,346
Weighted-average yield After 5 to 10 years	1.74%	1.70%
Amortized cost After 10 years	$ 979,366	$ 1,047,298
Gross Unrealized Gains After 10 years	16	83
Gross Unrealized Losses After 10 years	159,560	156,344
Allowance for Credit Losses After 10 years	0	0
Fair value After 10 years	$ 819,822	$ 891,037
Weighted-average yield After 10 years	1.51%	1.37%
Amortized cost	$ 1,246,253	$ 1,373,279
Gross Unrealized Gains	16	83
Gross Unrealized Losses	179,123	180,913
Allowance for Credit Losses	0	0
Fair value	$ 1,067,146	$ 1,192,449
Weighted-average yield	1.56%	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	$ 377,812	$ 273,539
Gross Unrealized Gains After 10 years	74	0
Gross Unrealized Losses After 10 years	52,338	52,263
Allowance for Credit Losses After 10 years	0	0
Fair value After 10 years	$ 325,548	$ 221,276
Weighted-average yield After 10 years	2.88%	1.54%
Residential MBS [Member] | Private label [Member]
Schedule Of Available For Sale Securities [Line Items]
Amortized cost After 5 to 10 years	$ 4,886
Gross Unrealized Gains After 5 to 10 years	0
Gross Unrealized Losses After 5 to 10 years	1,430
Allowance for Credit Losses After 5 to 10 years	57
Fair value After 5 to 10 years	$ 3,399
Weighted-average yield After 5 to 10 years	6.69%
Amortized cost After 10 years	$ 1,200	$ 7,086
Gross Unrealized Gains After 10 years	0	0
Gross Unrealized Losses After 10 years	285	2,185
Allowance for Credit Losses After 10 years	119	116
Fair value After 10 years	$ 796	$ 4,785
Weighted-average yield After 10 years	6.32%	7.66%
Amortized cost	$ 6,086
Gross Unrealized Gains	0
Gross Unrealized Losses	1,715
Allowance for Credit Losses	176	$ 100
Fair value	$ 4,195
Weighted-average yield	6.62%	7.66%
Residential MBS [Member] | Private label [Member] | Available-for-Sale Securities [Member]
Schedule Of Available For Sale Securities [Line Items]
Allowance for Credit Losses	$ 176	$ 116	$ 83	$ 797
Commercial Mortgage Backed Securities [Member]
Schedule Of Available For Sale Securities [Line Items]
Amortized cost After 1 to 5 years	33,835	45,022
Gross Unrealized Gains After 1 to 5 years	13	0
Gross Unrealized Losses After 1 to 5 years	2,286	6,898
Allowance for Credit Losses After 1 to 5 years	0	0
Fair value After 1 to 5 years	$ 31,562	$ 38,124
Weighted-average yield After 1 to 5 years	2.59%	2.17%
Amortized cost After 5 to 10 years	$ 10,621	$ 22,386
Gross Unrealized Gains After 5 to 10 years	0	0
Gross Unrealized Losses After 5 to 10 years	1,653	2,685
Allowance for Credit Losses After 5 to 10 years	0	0
Fair value After 5 to 10 years	$ 8,968	$ 19,701
Weighted-average yield After 5 to 10 years	1.67%	2.16%
Amortized cost After 10 years	$ 178,537	$ 122,830
Gross Unrealized Gains After 10 years	0	0
Gross Unrealized Losses After 10 years	37,158	29,037
Allowance for Credit Losses After 10 years	0	0
Fair value After 10 years	$ 141,379	$ 93,793
Weighted-average yield After 10 years	2.06%	1.36%
Amortized cost	$ 222,993	$ 190,238
Gross Unrealized Gains	13	0
Gross Unrealized Losses	41,097	38,620
Allowance for Credit Losses	0	0
Fair value	$ 181,909	$ 151,618
Weighted-average yield	2.12%	1.64%
Mortgage Backed Securities [Member]
Schedule Of Available For Sale Securities [Line Items]
Amortized cost	$ 3,145,117	$ 3,259,377
Gross Unrealized Gains	144	193
Gross Unrealized Losses	481,923	474,675
Allowance for Credit Losses	176	116
Fair value	$ 2,663,162	$ 2,784,779
Weighted-average yield	1.82%	1.55%
Other Debt Obligations [Member]
Schedule Of Available For Sale Securities [Line Items]
Amortized cost Due within one year	$ 1,000
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	$ 1,000
Weighted-average yield Due within one year	2.32%
Uninsured Portion Of Government Deposits [Member] | Asset Pledged as Collateral [Member]
Schedule Of Available For Sale Securities [Line Items]
Amortized cost	$ 3,300,000	$ 3,200,000
Fair value	$ 3,000,000	$ 2,800,000