XML 33 R17.htm IDEA: XBRL DOCUMENT
v3.25.4

Other Borrowed Funds | 12 Months Ended
--- | ---
Dec. 31, 2025
Other Borrowed Funds |
Other Borrowed Funds | (8) Other Borrowed Funds Other borrowed funds include Federal Home Loan Bank borrowings, which may be short, and long-term fixed borrowings issued by the Federal Home Loan Bank of Dallas and the Federal Home Loan Bank of Topeka at the market price offered at the time of funding. These borrowings are secured by mortgage-backed investment securities and a portion of our loan portfolio. Further information regarding our other borrowed funds at December 31, 2025 and 2024 is set forth in the following table:
​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
​ | ​ | December 31, |
​ | ​ | 2025 | ​ | 2024 |
​ | ​ | (Dollars in Thousands) |
Federal Home Loan Bank advances—short-term | ​ ​ ​ | ​ | ​ ​ ​ | ​ ​ ​ | ​ | ​ ​ ​ | ​
Average daily balance | ​ | $ | 44,575 | ​ | $ | — | ​
Average rate | ​ |  | 3.11 | % |  | — | %
Maximum amount outstanding at any month end | ​ | $ | 250,000 | ​ | $ | — | ​
Federal Home Loan Bank advances—long-term(1) | ​ | ​ | ​ | ​ | ​ | ​ | ​
Balance at year end | ​ | $ | 10,332 | ​ | $ | 10,541 | ​
Rate on balance outstanding at year end | ​ |  | 2.61 | % |  | 2.61 | %
Average daily balance | ​ | $ | 10,428 | ​ | $ | 10,635 | ​
Average rate | ​ |  | 2.61 | % |  | 2.61 | %
Maximum amount outstanding at any month end | ​ | $ | 10,524 | ​ | $ | 10,729 | ​
| (1) | Long-term advances at December 31, 2025 and December 31, 2024 consisted of amortizing advances. Two amortizing advances are outstanding at December 31, 2025 in the amounts of $2,788,000 and $7,544,000 and mature in December 2033 and November 2033, respectively. The amortization on the amortizing long-term advances totals approximately $215,000, $221,000, $227,000, $233,000 and $239,000 for the years ending December 31, 2026, 2027, 2028, 2029 and December 31, 2030, respectively.

X
- References No definition available. + Details
Name: | iboc_OtherBorrowedFundsDisclosureAbstract
Namespace Prefix: | iboc_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition The entire disclosure for borrowing from the Federal Home Loan Bank, including: (i) general description; (ii) title and nature of obligation; (iii) interest rate; (iv) payment terms; (v) maturity dates by year; (vi) collateral requirements; (vii) restrictive covenants; (viii) priority; (ix) conversion or redemption features; (x) carrying value of assets pledged as collateral; (xi) combined aggregate maturities for next five years; (xii) unused or available balances. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Topic 942 -SubTopic 210 -Name Accounting Standards Codification -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-03(13)(3)(a)) -Publisher FASB -URI https://asc.fasb.org/1943274/2147478546/942-210-S99-1 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Topic 942 -SubTopic 470 -Name Accounting Standards Codification -Section 45 -Paragraph 1 -Publisher FASB -URI https://asc.fasb.org/1943274/2147478878/942-470-45-1 Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Name Accounting Standards Codification -Topic 942 -SubTopic 470 -Section 50 -Paragraph 3 -Publisher FASB -URI https://asc.fasb.org/1943274/2147477734/942-470-50-3 Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef -Name Accounting Standards Codification -Section 50 -Paragraph 1 -SubTopic 10 -Topic 470 -Publisher FASB -URI https://asc.fasb.org/1943274/2147481544/470-10-50-1 + Details
Name: | us-gaap_FederalHomeLoanBankAdvancesDisclosureTextBlock
Namespace Prefix: | us-gaap_
Data Type: | dtr-types:textBlockItemType
Balance Type: | na
Period Type: | duration