DEBT SECURITIES (Tables)	3 Months Ended
DEBT SECURITIES (Tables)	Mar. 31, 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 March 31, 2024 2023 Private label MBS Puerto Rico Government Obligation Total Private label MBS Puerto Rico Government Obligation Total (In thousands) Beginning balance $ 116 $ 395 $ 511 $ 83 $ 375 $ 458 Provision for credit losses – benefit - (69) (69) - (9) (9) ACL on available-for-sale debt securities $ 116 $ 326 $ 442 $ 83 $ 366 $ 449
Debt Securities, Held-to-maturity, Allowance for Credit Loss [Table Text Block]	Puerto Rico Municipal Bonds Quarter Ended March 31, 2024 2023 (In thousands) Beginning balance $ 2,197 $ 8,286 Provision for credit losses – benefit (962) (640) ACL on held-to-maturity debt securities $ 1,235 $ 7,646
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]	March 31, 2024 Amortized cost (1) Gross ACL Fair value (2) Unrealized Weighted- Gains Losses average yield% (Dollars in thousands) U.S. Treasury securities: Due within one year $ 100,519 $ - $ 3,144 $ - $ 97,375 0.70 After 1 to 5 years 19,881 - 1,188 - 18,693 0.65 U.S. government-sponsored entities' (“GSEs”) obligations: Due within one year 683,768 - 17,920 - 665,848 0.90 After 1 to 5 years 1,698,700 59 128,048 - 1,570,711 0.82 After 5 to 10 years 8,850 - 754 - 8,096 2.64 After 10 years 8,762 3 4 - 8,761 5.51 Puerto Rico government obligation: After 10 years (3) 3,112 - 1,235 326 1,551 - United States and Puerto Rico government obligations 2,523,592 62 152,293 326 2,371,035 0.86 Mortgage-backed securities (“MBS”): Residential MBS: FHLMC certificates: Due within one year 7 - - - 7 4.50 After 1 to 5 years 17,827 - 856 - 16,971 2.06 After 5 to 10 years 146,335 - 13,488 - 132,847 1.55 After 10 years 970,917 8 169,069 - 801,856 1.41 1,135,086 8 183,413 - 951,681 1.44 GNMA certificates: Due within one year 281 - 3 - 278 3.25 After 1 to 5 years 14,493 - 789 - 13,704 1.11 After 5 to 10 years 26,563 4 2,387 - 24,180 1.65 After 10 years 201,129 165 25,748 - 175,546 2.60 242,466 169 28,927 - 213,708 2.41 FNMA certificates: After 1 to 5 years 29,694 - 1,411 - 28,283 2.11 After 5 to 10 years 284,547 - 24,926 - 259,621 1.73 After 10 years 1,016,944 32 161,363 - 855,613 1.36 1,331,185 32 187,700 - 1,143,517 1.46 Collateralized mortgage obligations (“CMOs”) issued or guaranteed by the FHLMC, FNMA, and GNMA: After 10 years 267,401 - 53,977 - 213,424 1.54 Private label: After 5 to 10 years 400 - 93 2 305 8.44 After 10 years 6,496 - 1,963 114 4,419 7.58 6,896 - 2,056 116 4,724 7.63 Total Residential MBS 2,983,034 209 456,073 116 2,527,054 1.55 Commercial MBS: After 1 to 5 years 44,443 2 7,044 - 37,401 2.18 After 5 to 10 years 22,252 - 2,785 - 19,467 2.16 After 10 years 122,164 - 29,942 - 92,222 1.36 Total Commercial MBS 188,859 2 39,771 - 149,090 1.64 Total MBS 3,171,893 211 495,844 116 2,676,144 1.55 Total available-for-sale debt securities $ 5,695,485 $ 273 $ 648,137 $ 442 $ 5,047,179 1.25 (1) Excludes accrued interest receivable on available-for-sale debt securities that totaled $ 10.2 million as of March 31, 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 $ 473 .0 million (amortized cost - $ 552.3 million) that was pledged at the FHLB as collateral for borrowings and letters of credit as well as $ 2.8 billion (amortized cost - $ 3.1 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 ACL Fair value (2) Unrealized 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 March 31,2024 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 $ 4,238 $ 5 $ 2,354,777 $ 151,053 $ 2,359,015 $ 151,058 Puerto Rico government obligation - - 1,551 1,235 (1) 1,551 1,235 MBS: Residential MBS: FHLMC 7 - 950,687 183,413 950,694 183,413 GNMA 3,452 20 195,424 28,907 198,876 28,927 FNMA 3,963 11 1,134,624 187,689 1,138,587 187,700 CMOs issued or guaranteed by the FHLMC, FNMA, and GNMA - - 211,178 53,977 211,178 53,977 Private label - - 4,724 2,056 (1) 4,724 2,056 Commercial MBS 5,346 65 137,794 39,706 143,140 39,771 $ 17,006 $ 101 $ 4,990,759 $ 648,036 $ 5,007,765 $ 648,137 (1) Unrealized losses do not include the credit loss component recorded as part of the ACL. As of March 31,2024, the PRHFA bond and private label MBS had an ACL of $ 0.3 million and $ 0.1 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]	March 31,2024 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 $ 3,172 $ 4 $ 16 $ 3,160 $ 36 9.30 After 1 to 5 years 51,327 713 831 51,209 460 7.74 After 5 to 10 years 36,034 3,135 257 38,912 450 7.06 After 10 years 16,595 23 16 16,602 289 8.81 Total Puerto Rico municipal bonds 107,128 3,875 1,120 109,883 1,235 7.72 MBS: Residential MBS: FHLMC certificates: After 5 to 10 years 15,337 - 626 14,711 - 3.03 After 10 years 18,165 - 1,025 17,140 - 4.33 33,502 - 1,651 31,851 - 3.74 GNMA certificates: After 10 years 15,649 - 910 14,739 - 3.30 FNMA certificates: After 10 years 66,109 - 3,504 62,605 - 4.18 CMOs issued or guaranteed by FHLMC, FNMA, and GNMA: After 10 years 27,417 - 1,584 25,833 - 3.49 Total Residential MBS 142,677 - 7,649 135,028 - 3.85 Commercial MBS: After 1 to 5 years 9,397 - 334 9,063 - 3.48 After 10 years 90,128 - 5,982 84,146 - 3.15 Total Commercial MBS 99,525 - 6,316 93,209 - 3.18 Total MBS 242,202 - 13,965 228,237 - 3.57 Total held-to-maturity debt securities $ 349,330 $ 3,875 $ 15,085 $ 338,120 $ 1,235 4.85 (1) Excludes accrued interest receivable on held-to-maturity debt securities that totaled $ 2.8 million as of March 31,2024 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 $ 126.2 million (fair value - $ 125.5 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 March 31,2024 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 $ - $ - $ 31,125 $ 1,120 $ 31,125 $ 1,120 MBS: Residential MBS: FHLMC certificates - - 31,851 1,651 31,851 1,651 GNMA certificates - - 14,739 910 14,739 910 FNMA certificates - - 62,605 3,504 62,605 3,504 CMOs issued or guaranteed by FHLMC, FNMA, and GNMA - - 25,833 1,584 25,833 1,584 Commercial MBS - - 93,209 6,316 93,209 6,316 Total held-to-maturity debt securities $ - $ - $ 259,362 $ 15,085 $ 259,362 $ 15,085 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