DEBT SECURITIES (Tables)	9 Months Ended
DEBT SECURITIES (Tables)	Sep. 30, 2024
Other Than Temporary Impairment Credit Losses Recognized In Earnings [Line Items]
Debt Securities, Available-for-sale, Allowance for Credit Loss [Table Text Block]	Quarter Ended September 30, 2024 2023 Private label MBS Puerto Rico Government Obligation Total Private label MBS Puerto Rico Government Obligation Total (In thousands) Beginning balance $ 163 $ 386 $ 549 $ 83 $ 350 $ 433 Provision for credit losses – (benefit) expense - (36) (36) - 32 32 Net recoveries 13 - 13 - - - ACL on available-for-sale debt securities $ 176 $ 350 $ 526 $ 83 $ 382 $ 465 Nine-Month Period Ended September 30, 2024 2023 Private label MBS Puerto Rico Government Obligations Total Private label MBS Puerto Rico Government Obligations Total (In thousands) Beginning balance $ 116 $ 395 $ 511 $ 83 $ 375 $ 458 Provision for credit losses - (benefit) expense - (45) (45) - 7 7 Net recoveries 60 - 60 - - - ACL on available-for-sale debt securities $ 176 $ 350 $ 526 $ 83 $ 382 $ 465
Debt Securities, Held-to-maturity, Allowance for Credit Loss [Table Text Block]	Puerto Rico Municipal Bonds Quarter Ended September 30, 2024 2023 (In thousands) Beginning balance $ 1,267 $ 8,401 Provision for credit losses – benefit (148) (6,151) ACL on held-to-maturity debt securities $ 1,119 $ 2,250 Puerto Rico Municipal Bonds Nine-Month Period Ended September 30, 2024 2023 (In thousands) Beginning Balance $ 2,197 $ 8,286 Provision for credit losses - benefit (1,078) (6,036) ACL on held-to-maturity debt securities $ 1,119 $ 2,250
Available-for-sale Securities [Member]
Other Than Temporary Impairment Credit Losses Recognized In Earnings [Line Items]
Investments Classified by Contractual Maturity Date [Table Text Block]	September 30, 2024 Amortized cost (1) Gross Unrealized ACL Fair Value (2) Weighted- Gains Losses average yield% (Dollars in thousands) U.S. Treasury securities: Due within one year $ 100,140 $ - $ 1,528 $ - $ 98,612 0.74 U.S. government-sponsored entities' (“GSEs”) obligations: Due within one year 954,478 - 15,323 - 939,155 0.83 After 1 to 5 years 1,281,265 51 65,467 - 1,215,849 0.85 After 10 years 8,155 10 4 - 8,161 5.21 Puerto Rico government obligation: After 10 years (3) 3,008 - 1,091 350 1,567 - United States and Puerto Rico government obligations 2,347,046 61 83,413 350 2,263,344 0.85 Mortgage-backed securities (“MBS”): Residential MBS: Freddie Mac (“FHLMC”) certificates: Due within one year 2 - - - 2 4.04 After 1 to 5 years 14,626 - 435 - 14,191 2.06 After 5 to 10 years 131,333 - 8,652 - 122,681 1.54 After 10 years 922,868 34 135,996 - 786,906 1.40 1,068,829 34 145,083 - 923,780 1.43 Ginnie Mae (“GNMA”) certificates: Due within one year 1,493 - 13 - 1,480 2.77 After 1 to 5 years 9,137 - 396 - 8,741 0.70 After 5 to 10 years 60,779 7 3,846 - 56,940 1.91 After 10 years 155,215 428 17,212 - 138,431 2.75 226,624 435 21,467 - 205,592 2.44 Fannie Mae (“FNMA”) certificates: After 1 to 5 years 24,395 - 698 - 23,697 2.12 After 5 to 10 years 258,732 - 15,835 - 242,897 1.74 After 10 years 961,208 160 128,052 - 833,316 1.35 1,244,335 160 144,585 - 1,099,910 1.45 Collateralized mortgage obligations (“CMOs”) issued or guaranteed by the FHLMC, FNMA, and GNMA: After 10 years 251,397 3 46,471 - 204,929 1.49 Private label: After 5 to 10 years 2,528 - 727 7 1,794 7.39 After 10 years 3,817 - 1,121 169 2,527 6.60 6,345 - 1,848 176 4,321 6.92 Total Residential MBS 2,797,530 632 359,454 176 2,438,532 1.54 Commercial MBS: After 1 to 5 years 34,010 9 1,879 - 32,140 2.69 After 5 to 10 years 13,241 - 1,464 - 11,777 2.02 After 10 years 179,730 492 32,234 - 147,988 2.06 Total Commercial MBS 226,981 501 35,577 - 191,905 2.15 Total MBS 3,024,511 1,133 395,031 176 2,630,437 1.58 Other: Due within one year 500 - - - 500 2.34 After 1 to 5 years 500 - - - 500 2.34 1,000 - - - 1,000 2.34 Total available-for-sale debt securities $ 5,372,557 $ 1,194 $ 478,444 $ 526 $ 4,894,781 1.26 (1) Excludes accrued interest receivable on available-for-sale debt securities that totaled $ 9.5 million as of September 30, 2024 reported as part of accrued interest receivable on loans and investment securities in the consolidated statements of financial condition, and excluded from the estimate of credit losses. (2) Includes $ 475.1 million (amortized cost - $ 532.2 million) that was pledged at the FHLB as collateral for borrowings and letters of credit as well as $ 2.7 billion (amortized cost - $ 3.0 billion) pledged as collateral for the uninsured portion of government deposits. The secured parties are not permitted to sell or repledge the collateral. (3) Consists of a residential pass-through MBS issued by the Puerto Rico Housing Finance Authority (the “PRHFA”) that is collateralized by certain second mortgages originated under a program launched by the Puerto Rico government in 2010 and is in nonaccrual status based on the delinquency status of the underlying second mortgage loans collateral. December 31, 2023 Amortized cost (1) Gross Unrealized ACL Fair value (2) Weighted- Gains Losses average yield% (Dollars in thousands) U.S. Treasury securities: Due within one year $ 80,314 $ - $ 2,144 $ - $ 78,170 0.66 After 1 to 5 years 60,239 - 3,016 - 57,223 0.75 U.S. GSEs’ obligations: Due within one year 542,847 - 15,832 - 527,015 0.77 After 1 to 5 years 1,899,620 49 135,347 - 1,764,322 0.86 After 5 to 10 years 8,850 - 687 - 8,163 2.64 After 10 years 8,891 8 2 - 8,897 5.49 Puerto Rico government obligation: After 10 years (3) 3,156 - 1,346 395 1,415 - United States and Puerto Rico government obligations 2,603,917 57 158,374 395 2,445,205 0.85 MBS: Residential MBS: FHLMC certificates: After 1 to 5 years 19,561 - 868 - 18,693 2.06 After 5 to 10 years 153,308 - 12,721 - 140,587 1.55 After 10 years 991,060 15 161,197 - 829,878 1.41 1,163,929 15 174,786 - 989,158 1.44 GNMA certificates: Due within one year 254 - 3 - 251 3.27 After 1 to 5 years 16,882 - 872 - 16,010 1.19 After 5 to 10 years 27,916 8 2,247 - 25,677 1.62 After 10 years 206,254 87 22,786 - 183,555 2.57 251,306 95 25,908 - 225,493 2.38 FNMA certificates: After 1 to 5 years 32,489 - 1,423 - 31,066 2.11 After 5 to 10 years 293,492 - 23,146 - 270,346 1.70 After 10 years 1,047,298 83 156,344 - 891,037 1.37 1,373,279 83 180,913 - 1,192,449 1.46 CMOs issued or guaranteed by the FHLMC, FNMA, and GNMA: After 10 years 273,539 - 52,263 - 221,276 1.54 Private label: After 10 years 7,086 - 2,185 116 4,785 7.66 Total Residential MBS 3,069,139 193 436,055 116 2,633,161 1.55 Commercial MBS: After 1 to 5 years 45,022 - 6,898 - 38,124 2.17 After 5 to 10 years 22,386 - 2,685 - 19,701 2.16 After 10 years 122,830 - 29,037 - 93,793 1.36 Total Commercial MBS 190,238 - 38,620 - 151,618 1.64 Total MBS 3,259,377 193 474,675 116 2,784,779 1.55 Total available-for-sale debt securities $ 5,863,294 $ 250 $ 633,049 $ 511 $ 5,229,984 1.24 (1) Excludes accrued interest receivable on available-for-sale debt securities that totaled $ 10.6 million as of December 31, 2023 reported as part of accrued interest receivable on loans and investment securities in the consolidated statements of financial condition, and excluded from the estimate of credit losses. (2) Includes $ 477.9 million (amortized cost - $ 527.2 million) that was pledged at the FHLB as collateral for borrowings and letters of credit as well as $ 2.8 billion (amortized cost - $ 3.2 billion) pledged as collateral for the uninsured portion of government deposits. The secured parties are not permitted to sell or repledge the collateral. (3) Consists of a residential pass-through MBS issued by the PRHFA that is collateralized by certain second mortgages originated under a program launched by the Puerto Rico government in 2010 and is in nonaccrual status based on the delinquency status of the underlying second mortgage loans collateral.
Schedule of Unrealized Loss on Investments [Table Text Block]	As of September 30, 2024 Less than 12 months 12 months or more Total Unrealized Unrealized Unrealized Fair Value Losses Fair Value Losses Fair Value Losses (In thousands) U.S. Treasury and U.S. GSEs’ obligations $ 1,828 $ 4 $ 2,247,894 $ 82,318 $ 2,249,722 $ 82,322 Puerto Rico government obligation - - 1,567 1,091 (1) 1,567 1,091 MBS: Residential MBS: FHLMC 2 - 921,769 145,083 921,771 145,083 GNMA 69 1 180,162 21,466 180,231 21,467 FNMA - - 1,090,120 144,585 1,090,120 144,585 CMOs issued or guaranteed by the FHLMC, FNMA, and GNMA - - 199,741 46,471 199,741 46,471 Private label - - 4,321 1,848 (1) 4,321 1,848 Commercial MBS 8,869 174 139,632 35,403 148,501 35,577 $ 10,768 $ 179 $ 4,785,206 $ 478,265 $ 4,795,974 $ 478,444 (1) Unrealized losses do not include the credit loss component recorded as part of the ACL. As of September 30, 2024, the PRHFA bond and private label MBS had an ACL of $ 0.3 million and $ 0.2 million, respectively. As of December 31, 2023 Less than 12 months 12 months or more Total Unrealized Unrealized Unrealized Fair Value Losses Fair Value Losses Fair Value Losses (In thousands) U.S. Treasury and U.S. GSEs’ obligations $ 2,544 $ 2 $ 2,428,784 $ 157,026 $ 2,431,328 $ 157,028 Puerto Rico government obligation - - 1,415 1,346 (1) 1,415 1,346 MBS: Residential MBS: FHLMC 9 - 988,092 174,786 988,101 174,786 GNMA 12,257 100 202,390 25,808 214,647 25,908 FNMA - - 1,183,275 180,913 1,183,275 180,913 CMOs issued or guaranteed by the FHLMC, FNMA, and GNMA - - 221,276 52,263 221,276 52,263 Private label - - 4,785 2,185 (1) 4,785 2,185 Commercial MBS 11,370 18 140,248 38,602 151,618 38,620 $ 26,180 $ 120 $ 5,170,265 $ 632,929 $ 5,196,445 $ 633,049 (1) Unrealized losses do not include the credit loss component recorded as part of the ACL. As of December 31, 2023, the PRHFA bond and private label MBS had an ACL of $ 0.4 million and $ 0.1 million, respectively.
Held-to-maturity Securities [Member]
Other Than Temporary Impairment Credit Losses Recognized In Earnings [Line Items]
Investments Classified by Contractual Maturity Date [Table Text Block]	September 30, 2024 Amortized cost (1) (2) Gross Unrecognized Fair value Weighted- Gains Losses ACL average yield% (Dollars in thousands) Puerto Rico municipal bonds: Due within one year $ 2,131 $ 196 $ 10 $ 2,317 $ 9 5.62 After 1 to 5 years 61,119 2,471 457 63,133 662 7.81 After 5 to 10 years 13,121 679 229 13,571 189 6.42 After 10 years 15,755 - 170 15,585 259 8.80 Total Puerto Rico municipal bonds 92,126 3,346 866 94,606 1,119 7.73 MBS: Residential MBS: FHLMC certificates: After 5 to 10 years 13,084 - 250 12,834 - 3.03 After 10 years 17,281 - 448 16,833 - 4.31 30,365 - 698 29,667 - 3.76 GNMA certificates: After 10 years 14,313 - 432 13,881 - 3.31 FNMA certificates: After 10 years 62,754 - 1,545 61,209 - 4.18 CMOs issued or guaranteed by FHLMC, FNMA, and GNMA: After 10 years 26,420 - 914 25,506 - 3.49 Total Residential MBS 133,852 - 3,589 130,263 - 3.86 Commercial MBS: After 1 to 5 years 9,306 - 124 9,182 - 3.48 After 10 years 87,858 - 5,055 82,803 - 3.15 Total Commercial MBS 97,164 - 5,179 91,985 - 3.18 Total MBS 231,016 - 8,768 222,248 - 3.57 Total held-to-maturity debt securities $ 323,142 $ 3,346 $ 9,634 $ 316,854 $ 1,119 4.76 (1) Excludes accrued interest receivable on held-to-maturity debt securities that totaled $ 2.5 million as of September 30, 2024 reported as part of accrued interest receivable on loans and investment securities in the consolidated statements of financial condition, and excluded from the estimate of credit losses. (2) Includes $ 199.1 million (fair value - $ 194.3 million) that serves as collateral for the uninsured portion of government deposits. The secured parties are not permitted to sell or repledge the collateral. December 31, 2023 Amortized cost (1) (2) Gross Unrecognized Fair value Weighted- Gains Losses ACL average yield% (Dollars in thousands) Puerto Rico municipal bonds: Due within one year $ 3,165 $ 8 $ 38 $ 3,135 $ 50 9.30 After 1 to 5 years 51,230 994 710 51,514 1,266 7.78 After 5 to 10 years 36,050 3,540 210 39,380 604 7.13 After 10 years 16,595 269 - 16,864 277 8.87 Total Puerto Rico municipal bonds 107,040 4,811 958 110,893 2,197 7.78 MBS: Residential MBS: FHLMC certificates: After 5 to 10 years 16,469 - 556 15,913 - 3.03 After 10 years 18,324 - 714 17,610 - 4.32 34,793 - 1,270 33,523 - 3.71 GNMA certificates: After 10 years 16,265 - 789 15,476 - 3.32 FNMA certificates: After 10 years 67,271 - 2,486 64,785 - 4.18 CMOs issued or guaranteed by FHLMC, FNMA, and GNMA: After 10 years 28,139 - 1,274 26,865 - 3.49 Total Residential MBS 146,468 - 5,819 140,649 - 3.84 Commercial MBS: After 1 to 5 years 9,444 - 297 9,147 - 3.48 After 10 years 91,226 - 5,783 85,443 - 3.15 Total Commercial MBS 100,670 - 6,080 94,590 - 3.18 Total MBS 247,138 - 11,899 235,239 - 3.57 Total held-to-maturity debt securities $ 354,178 $ 4,811 $ 12,857 $ 346,132 $ 2,197 4.84 (1) Excludes accrued interest receivable on held-to-maturity debt securities that totaled $ 4.8 million as of December 31, 2023 reported as part of accrued interest receivable on loans and investment securities in the consolidated statements of financial condition, and excluded from the estimate of credit losses. (2) Includes $ 126.6 million (fair value - $ 125.9 million) that serves as collateral for the uninsured portion of government deposits. The secured parties are not permitted to sell or repledge the collateral.
Schedule of Unrealized Loss on Investments [Table Text Block]	As of September 30, 2024 Less than 12 months 12 months or more Total Unrecognized Unrecognized Unrecognized Fair Value Losses Fair Value Losses Fair Value Losses (In thousands) Puerto Rico municipal bonds $ - $ - $ 43,997 $ 866 $ 43,997 $ 866 MBS: Residential MBS: FHLMC certificates - - 29,667 698 29,667 698 GNMA certificates - - 13,881 432 13,881 432 FNMA certificates - - 61,209 1,545 61,209 1,545 CMOs issued or guaranteed by FHLMC, FNMA, and GNMA - - 25,506 914 25,506 914 Commercial MBS - - 91,985 5,179 91,985 5,179 Total held-to-maturity debt securities $ - $ - $ 266,245 $ 9,634 $ 266,245 $ 9,634 As of December 31, 2023 Less than 12 months 12 months or more Total Unrecognized Unrecognized Unrecognized Fair Value Losses Fair Value Losses Fair Value Losses (In thousands) Puerto Rico municipal bonds $ - $ - $ 34,682 $ 958 $ 34,682 $ 958 MBS: Residential MBS: FHLMC certificates - - 33,523 1,270 33,523 1,270 GNMA certificates - - 15,476 789 15,476 789 FNMA certificates - - 64,785 2,486 64,785 2,486 CMOs issued or guaranteed by FHLMC, FNMA, and GNMA - - 26,865 1,274 26,865 1,274 Commercial MBS - - 94,590 6,080 94,590 6,080 Total held-to-maturity debt securities $ - $ - $ 269,921 $ 12,857 $ 269,921 $ 12,857