DEBT SECURITIES (Tables)	9 Months Ended
DEBT SECURITIES (Tables)	Sep. 30, 2025
Other Than Temporary Impairment Credit Losses Recognized In Earnings [Line Items]
ACL on Available-for-Sale Debt Securities [Table Text Block]	Quarter Ended September 30, 2025 2024 Private label MBS Puerto Rico Government Obligation Total Private label MBS Puerto Rico Government Obligation Total (In thousands) Beginning balance $ 176 $ 337 $ 513 $ 163 $ 386 $ 549 Provision for credit losses – expense (benefit) 155 (9) 146 - (36) (36) Net (charge-offs) recoveries (1) - (1) 13 - 13 ACL on available-for-sale debt securities $ 330 $ 328 $ 658 $ 176 $ 350 $ 526 Nine-Month Period Ended September 30, 2025 2024 Private label MBS Puerto Rico Government Obligation Total Private label MBS Puerto Rico Government Obligation Total (In thousands) Beginning balance $ 176 $ 345 $ 521 $ 116 $ 395 $ 511 Provision for credit losses - expense (benefit) 155 (17) 138 - (45) (45) Net (charge-offs) recoveries (1) - (1) 60 - 60 ACL on available-for-sale debt securities $ 330 $ 328 $ 658 $ 176 $ 350 $ 526
ACL on Held-to-Maturity Debt Securities [Table Text Block]	Government Bonds Quarter Ended September 30, 2025 2024 (In thousands) Beginning balance $ 765 $ 1,267 Provision for credit losses – benefit (67) (148) ACL on held-to-maturity debt securities $ 698 $ 1,119 Government Bonds Nine-Month Period Ended September 30, 2025 2024 (In thousands) Beginning Balance $ 802 $ 2,197 Provision for credit losses - benefit (104) (1,078) ACL on held-to-maturity debt securities $ 698 $ 1,119
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, 2025 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 $ 496,714 $ 94 $ 5 $ - $ 496,803 4.11 U.S. government-sponsored entities' (“GSEs”) obligations: Due within one year 775,287 25 6,302 - 769,010 0.80 After 1 to 5 years 506,086 - 22,532 - 483,554 0.92 After 10 years 6,909 - 59 - 6,850 4.47 Puerto Rico government obligation: After 10 years (3) 2,753 - 846 328 1,579 - United States and Puerto Rico government obligations 1,787,749 119 29,744 328 1,757,796 1.77 Mortgage-backed securities (“MBS”): Residential MBS: Freddie Mac (“FHLMC”) certificates: Due within one year 96 - - - 96 2.16 After 1 to 5 years 9,720 - 189 - 9,531 2.14 After 5 to 10 years 154,316 - 11,704 - 142,612 1.39 After 10 years 821,743 552 122,155 - 700,140 1.60 985,875 552 134,048 - 852,379 1.57 Ginnie Mae (“GNMA”) certificates: Due within one year 2 - - - 2 6.14 After 1 to 5 years 4,867 - 139 - 4,728 0.73 After 5 to 10 years 56,815 8 3,755 - 53,068 1.67 After 10 years 165,106 636 17,219 - 148,523 3.37 226,790 644 21,113 - 206,321 2.89 Fannie Mae (“FNMA”) certificates: Due within one year 123 - - - 123 1.30 After 1 to 5 years 14,749 - 280 - 14,469 2.15 After 5 to 10 years 294,158 72 20,580 - 273,650 1.61 After 10 years 809,915 711 105,828 - 704,798 1.56 1,118,945 783 126,688 - 993,040 1.58 Collateralized mortgage obligations (“CMOs”) issued or guaranteed by the FHLMC, FNMA, and GNMA: After 10 years 624,637 2,875 40,829 - 586,683 3.76 Private label: After 5 to 10 years 5,298 - 1,636 330 3,332 6.25 Total Residential MBS 2,961,545 4,854 324,314 330 2,641,755 2.15 Commercial MBS: After 1 to 5 years 33,316 9 1,348 - 31,977 2.52 After 5 to 10 years 10,409 - 1,189 - 9,220 1.68 After 10 years 190,927 195 34,067 - 157,055 2.39 Total Commercial MBS 234,652 204 36,604 - 198,252 2.37 Total MBS 3,196,197 5,058 360,918 330 2,840,007 2.16 Other: Due within one year 500 - - - 500 2.34 Total available-for-sale debt securities $ 4,984,446 $ 5,177 $ 390,662 $ 658 $ 4,598,303 2.02 (1) Excludes accrued interest receivable on available-for-sale debt securities that totaled $ 9.4 million as of September 30, 2025 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 $ 264.9 million (amortized cost - $ 301.2 million) that was pledged at the FHLB as collateral for borrowings and letters of credit as well as $ 2.9 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, 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 $ 59,992 $ - $ 803 $ - $ 59,189 0.75 U.S. GSEs’ obligations: Due within one year 1,090,678 - 22,826 - 1,067,852 0.79 After 1 to 5 years 817,835 39 53,195 - 764,679 0.96 After 10 years 7,835 - 35 - 7,800 4.73 Puerto Rico government obligation: After 10 years (3) 2,951 - 986 345 1,620 - United States and Puerto Rico government obligations 1,979,291 39 77,845 345 1,901,140 0.87 MBS: Residential MBS: FHLMC certificates: After 1 to 5 years 14,477 - 460 - 14,017 2.14 After 5 to 10 years 122,548 - 9,977 - 112,571 1.52 After 10 years 936,531 25 168,691 - 767,865 1.51 1,073,556 25 179,128 - 894,453 1.52 GNMA certificates: Due within one year 881 - 6 - 875 2.68 After 1 to 5 years 8,025 - 350 - 7,675 0.71 After 5 to 10 years 67,181 - 6,125 - 61,056 1.86 After 10 years 142,330 16 22,041 - 120,305 2.78 218,417 16 28,522 - 189,911 2.42 FNMA certificates: After 1 to 5 years 21,921 - 689 - 21,232 2.13 After 5 to 10 years 244,966 - 18,874 - 226,092 1.74 After 10 years 979,366 16 159,560 - 819,822 1.51 1,246,253 16 179,123 - 1,067,146 1.56 CMOs issued or guaranteed by the FHLMC, FNMA, and GNMA: After 10 years 377,812 74 52,338 - 325,548 2.88 Private label: After 5 to 10 years 4,886 - 1,430 57 3,399 6.69 After 10 years 1,200 - 285 119 796 6.32 6,086 - 1,715 176 4,195 6.62 Total Residential MBS 2,922,124 131 440,826 176 2,481,253 1.79 Commercial MBS: After 1 to 5 years 33,835 13 2,286 - 31,562 2.59 After 5 to 10 years 10,621 - 1,653 - 8,968 1.67 After 10 years 178,537 - 37,158 - 141,379 2.06 Total Commercial MBS 222,993 13 41,097 - 181,909 2.12 Total MBS 3,145,117 144 481,923 176 2,663,162 1.82 Other Due within one year 1,000 - - - 1,000 2.32 Total available-for-sale debt securities $ 5,125,408 $ 183 $ 559,768 $ 521 $ 4,565,302 1.45 (1) Excludes accrued interest receivable on available-for-sale debt securities that totaled $ 9.6 million as of December 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 $ 466.1 million (amortized cost - $ 533.7 million) that was pledged at the FHLB as collateral for borrowings and letters of credit as well as $ 3.0 billion (amortized cost - $ 3.3 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.
Investments Fair Value and Gross Unrealized Losses [Table Text Block]	As of September 30, 2025 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 $ 156,093 $ 61 $ 1,247,412 $ 28,837 $ 1,403,505 $ 28,898 Puerto Rico government obligation - - 1,579 846 (1) 1,579 846 MBS: Residential MBS: FHLMC - - 809,506 134,048 809,506 134,048 GNMA 20,286 148 158,847 20,965 179,133 21,113 FNMA - - 938,952 126,688 938,952 126,688 CMOs issued or guaranteed by the FHLMC, FNMA, and GNMA 40,999 159 174,556 40,670 215,555 40,829 Private label - - 3,332 1,636 (1) 3,332 1,636 Commercial MBS 7,764 163 139,350 36,441 147,114 36,604 $ 225,142 $ 531 $ 3,473,534 $ 390,131 $ 3,698,676 $ 390,662 (1) Unrealized losses do not include the credit loss component recorded as part of the ACL. As of September 30, 2025, the PRHFA bond and private label MBS had an ACL of $ 0.3 million and $0.4 million, respectively. As of December 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 $ 8,005 $ 35 $ 1,886,046 $ 76,824 $ 1,894,051 $ 76,859 Puerto Rico government obligation - - 1,620 986 (1) 1,620 986 MBS: Residential MBS: FHLMC 36,224 85 857,492 179,043 893,716 179,128 GNMA 22,281 508 166,470 28,014 188,751 28,522 FNMA 53,325 132 1,012,331 178,991 1,065,656 179,123 CMOs issued or guaranteed by the FHLMC, FNMA, and GNMA 52,778 248 187,772 52,090 240,550 52,338 Private label - - 4,195 1,715 (1) 4,195 1,715 Commercial MBS 44,831 823 131,152 40,274 175,983 41,097 $ 217,444 $ 1,831 $ 4,247,078 $ 557,937 $ 4,464,522 $ 559,768 (1) Unrealized losses do not include the credit loss component recorded as part of the ACL. As of December 31, 2024, the PRHFA bond and private label MBS had an ACL of $ 0.3 million and $ 0.2 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, 2025 Amortized cost (1) (2) Gross Unrecognized Fair value Weighted- Gains Losses ACL average yield% (Dollars in thousands) Government bonds: Due within one year $ 1,017 $ 64 $ 4 $ 1,077 $ 2 5.11 After 1 to 5 years 56,379 2,139 163 58,355 416 7.28 After 5 to 10 years 10,313 676 162 10,827 89 5.06 After 10 years 14,870 54 - 14,924 191 7.77 Total government bonds 82,579 2,933 329 85,183 698 7.06 MBS: Residential MBS: FHLMC certificates: After 1 to 5 years 9,214 - 142 9,072 - 3.03 After 10 years 15,826 - 543 15,283 - 4.31 25,040 - 685 24,355 - 3.84 GNMA certificates: After 10 years 11,577 - 438 11,139 - 3.29 FNMA certificates: After 5 to 10 years 9,583 - 392 9,191 - 3.11 After 10 years 46,977 - 1,392 45,585 - 4.41 56,560 - - 1,784 54,776 - 4.19 CMOs issued or guaranteed by FHLMC, FNMA, and GNMA: After 10 years 23,399 - 558 22,841 - 3.43 Total Residential MBS 116,576 - 3,465 113,111 - 3.87 Commercial MBS: Due within one year 9,112 - 41 9,071 - 3.48 After 10 years 65,096 - 3,208 61,888 - 1.94 Total Commercial MBS 74,208 - 3,249 70,959 - 2.13 Total MBS 190,784 - 6,714 184,070 - 3.20 Total held-to-maturity debt securities $ 273,363 $ 2,933 $ 7,043 $ 269,253 $ 698 4.36 (1) Excludes accrued interest receivable on held-to-maturity debt securities that totaled $ 2.0 million as of September 30, 2025 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 $ 204.7 million (fair value - $ 200.8 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, 2024 Amortized cost (1) (2) Gross Unrecognized Fair value Weighted- Gains Losses ACL average yield% (Dollars in thousands) Government bonds: Due within one year $ 2,214 $ 134 $ 6 $ 2,342 $ 6 5.07 After 1 to 5 years 61,289 2,724 438 63,575 433 7.33 After 5 to 10 years 13,184 811 205 13,790 127 5.79 After 10 years 15,755 146 - 15,901 236 8.07 Total government bonds 92,442 3,815 649 95,608 802 7.18 MBS: Residential MBS: FHLMC certificates: After 5 to 10 years 12,112 - 353 11,759 - 3.03 After 10 years 16,936 - 1,142 15,794 - 4.30 29,048 - 1,495 27,553 - 3.77 GNMA certificates: After 10 years 13,472 - 842 12,630 - 3.29 FNMA certificates: After 10 years 61,233 - 3,786 57,447 - 4.19 CMOs issued or guaranteed by FHLMC, FNMA, and GNMA: After 10 years 25,566 - 1,321 24,245 - 3.49 Total Residential MBS 129,319 - 7,444 121,875 - 3.86 Commercial MBS: After 1 to 5 years 9,258 - 151 9,107 - 3.48 After 10 years 86,767 - 5,317 81,450 - 3.92 Total Commercial MBS 96,025 - 5,468 90,557 - 3.88 Total MBS 225,344 - 12,912 212,432 - 3.87 Total held-to-maturity debt securities $ 317,786 $ 3,815 $ 13,561 $ 308,040 $ 802 4.83 (1) Excludes accrued interest receivable on held-to-maturity debt securities that totaled $ 4.1 million as of December 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 $ 198.6 million (fair value - $ 192.4 million) that serves as collateral for the uninsured portion of government deposits. The secured parties are not permitted to sell or repledge the collateral.
Investments Fair Value and Gross Unrealized Losses [Table Text Block]	As of September 30, 2025 Less than 12 months 12 months or more Total Unrecognized Unrecognized Unrecognized Fair Value Losses Fair Value Losses Fair Value Losses (In thousands) Government bonds $ - $ - $ 16,652 $ 329 $ 16,652 $ 329 MBS: Residential MBS: FHLMC certificates - - 24,355 685 24,355 685 GNMA certificates - - 11,139 438 11,139 438 FNMA certificates - - 54,776 1,784 54,776 1,784 CMOs issued or guaranteed by FHLMC, FNMA, and GNMA - - 22,841 558 22,841 558 Commercial MBS - - 70,959 3,249 70,959 3,249 Total held-to-maturity debt securities $ - $ - $ 200,722 $ 7,043 $ 200,722 $ 7,043 As of December 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) Government bonds $ - $ - $ 20,071 $ 649 $ 20,071 $ 649 MBS: Residential MBS: FHLMC certificates - - 27,553 1,495 27,553 1,495 GNMA certificates - - 12,630 842 12,630 842 FNMA certificates - - 57,447 3,786 57,447 3,786 CMOs issued or guaranteed by FHLMC, FNMA, and GNMA - - 24,245 1,321 24,245 1,321 Commercial MBS - - 90,557 5,468 90,557 5,468 Total held-to-maturity debt securities $ - $ - $ 232,503 $ 13,561 $ 232,503 $ 13,561