| Cover | 12 Months Ended |
| Dec. 31, 2022 | |
| Document Information [Line Items] | |
| Document Type | DEF 14A |
| Amendment Flag | false |
| Entity Information [Line Items] | |
| Entity Registrant Name | INTERNATIONAL BANCSHARES CORPORATION |
| Entity Central Index Key | 0000315709 |
| Pay vs Performance Disclosure | 12 Months Ended | ||
| Dec. 31, 2022 USD ($) | Dec. 31, 2021 USD ($) | Dec. 31, 2020 USD ($) | |
| Pay vs Performance Disclosure [Table] | |||
| Pay vs Performance [Table Text Block] | PAY VERSUS PERFORMANCE The following table (our “Pay-for-Performance Table”) reports the compensation of our principal executive officer (“PEO”) and the average compensation of our other NEOs for the past three fiscal years as reported in our Summary Compensation Table. The information reported in the Pay-for-Performance Table is meant to reflect the relationship between the executive compensation that the Company actually paid and certain measures of the Company’s financial performance. For information regarding the Company’s pay-for-performance philosophy and how we align executive compensation with the Company’s financial performance, refer to our CD&A. Year Summary (1) Compensation (3) Average (2) Average (3) Value of Initial Fixed $100 Net Income (6) Return on (7) Total (4) Peer Group (5) 2022 $ 2,403,081 $ 2,403,081 $ 321,179 $ 345,751 $ 132.27 $ 121.59 $ 300,232 12.52 % 2021 $ 2,882,996 $ 2,882,996 $ 255,396 $ 350,599 $ 119.68 $ 126.83 $ 253,922 11.28 % 2020 $ 2,142,783 $ 2,142,783 $ 219,848 $ 222,186 $ 102.72 $ 89.52 $ 167,318 7.86 % (1) Dennis E. Nixon, our PEO, was our CEO and Chairman for each of the years presented. (2) During 2021 and 2022, our non-PEO NEOs included Judith I. Wawroski (our PFO), Julie L. Tarvin, and Dalia F. Martinez. For 2020, our non-PEO NEOs included Judith I. Wawroski and Julie L. Tarvin, which reflects all of our non-PEO NEOs who received total compensation of at least $100,000. (3) Compensation “actually paid” is calculated in accordance with Item 402(v) of Regulation S-K. The table below sets forth each adjustment to the equity awards granted to our non-PEO NEOs during each year presented in the table to calculate the compensation actually paid to our non-PEO NEOs during each year. For each of the years presented in the table, the compensation paid to our PEO as reported in the Summary Compensation Table is the same as the compensation actually paid to our PEO because we did not grant any equity awards to our PEO. Accordingly, our PEO is excluded from the table below. Values reported in the table below are roundest to the nearest dollar. Non-PEO NEOs 2022 2021 2020 Average Summary Compensation Table Total $ 321,179 $ 255,396 $ 219,848 Deduction for amounts reported under the “Option Awards” –150,750 0 –6,113 Increase for fair value of awards granted during year that remain outstanding and unvested as of covered year end 141,210 0 130,099 Increase/deduction for change in fair value from prior year-end to covered year-end of awards granted prior to covered year that were outstanding and unvested as of covered year-end 35,986 32,810 –51,421 Increase/deduction for change in fair value from prior –1,874 62,393 –70,227 Total Adjustments $ 24,572 $ 95,203 $ 2,338 Compensation “Actually Paid” $ 345,751 $ 350,599 $ 222,186 (4) The amounts shown above represent the Company’s cumulative total shareholder return (“TSR”) on an assumed investment of $100 in shares of our Common Stock over the indicated measurement period. Cumulative TSR is calculated by dividing (i) the sum of the cumulative amount of dividends on our Common Stock for the measurement period (if any), assuming dividend reinvestment, and the difference between the Company’s share price at the end and the beginning of the measurement period, by (ii) the Company’s share price at the beginning of the measurement period. (5) The amounts shown above represent the cumulative peer group TSR on an assumed investment of $100, weighted according to the respective peer group companies’ stock market capitalization at the beginning of each period for which a return is indicated. The peer group used by the Company consists of the companies used in the Company’s performance graph as required by Item 201(e) of Regulation S-K and reported in the “Equity Compensation Plan Information” section of our audited financial statements for fiscal year 2022, which are included in Exhibit 13 to our Annual Report on Form 10-K; namely, the S&P 400 Bank Index. (6) The dollar amounts reported represent the amount of net income available to common shareholders reflected in the Company’s audited financial statements for the applicable year (in thousands). (7) The Company has identified return on average common equity (“ROE”), as adjusted for each year indicated as its Company-Selected Measure. Although the Company uses several financial and non-financial performance metrics to evaluate the Company’s performance for purposes of compensation programs, we believe ROE represents the most important financial performance measure that we used to link compensation actually paid to our PEO and non-PEO NEOs for the most recent fiscal year to the Company’s performance. | ||
| Company Selected Measure Name | Return on Average Common Equity | ||
| Named Executive Officers, Footnote [Text Block] | (1) Dennis E. Nixon, our PEO, was our CEO and Chairman for each of the years presented. (2) During 2021 and 2022, our non-PEO NEOs included Judith I. Wawroski (our PFO), Julie L. Tarvin, and Dalia F. Martinez. For 2020, our non-PEO NEOs included Judith I. Wawroski and Julie L. Tarvin, which reflects all of our non-PEO NEOs who received total compensation of at least $100,000. | ||
| Peer Group Issuers, Footnote [Text Block] | (5) The amounts shown above represent the cumulative peer group TSR on an assumed investment of $100, weighted according to the respective peer group companies’ stock market capitalization at the beginning of each period for which a return is indicated. The peer group used by the Company consists of the companies used in the Company’s performance graph as required by Item 201(e) of Regulation S-K and reported in the “Equity Compensation Plan Information” section of our audited financial statements for fiscal year 2022, which are included in Exhibit 13 to our Annual Report on Form 10-K; namely, the S&P 400 Bank Index. | ||
| PEO Total Compensation Amount | $ 2,403,081 | $ 2,882,996 | $ 2,142,783 |
| PEO Actually Paid Compensation Amount | 2,403,081 | 2,882,996 | 2,142,783 |
| Non-PEO NEO Average Total Compensation Amount | 321,179 | 255,396 | 219,848 |
| Non-PEO NEO Average Compensation Actually Paid Amount | $ 345,751 | 350,599 | 222,186 |
| Adjustment to Non-PEO NEO Compensation Footnote [Text Block] | (3) Compensation “actually paid” is calculated in accordance with Item 402(v) of Regulation S-K. The table below sets forth each adjustment to the equity awards granted to our non-PEO NEOs during each year presented in the table to calculate the compensation actually paid to our non-PEO NEOs during each year. For each of the years presented in the table, the compensation paid to our PEO as reported in the Summary Compensation Table is the same as the compensation actually paid to our PEO because we did not grant any equity awards to our PEO. Accordingly, our PEO is excluded from the table below. Values reported in the table below are roundest to the nearest dollar. Non-PEO NEOs 2022 2021 2020 Average Summary Compensation Table Total $ 321,179 $ 255,396 $ 219,848 Deduction for amounts reported under the “Option Awards” –150,750 0 –6,113 Increase for fair value of awards granted during year that remain outstanding and unvested as of covered year end 141,210 0 130,099 Increase/deduction for change in fair value from prior year-end to covered year-end of awards granted prior to covered year that were outstanding and unvested as of covered year-end 35,986 32,810 –51,421 Increase/deduction for change in fair value from prior –1,874 62,393 –70,227 Total Adjustments $ 24,572 $ 95,203 $ 2,338 Compensation “Actually Paid” $ 345,751 $ 350,599 $ 222,186 | ||
| Compensation Actually Paid vs. Net Income [Text Block] | PEO and Average Other NEOs Compensation Actually Paid vs. GAAP Net Income | ||
| Compensation Actually Paid vs. Company Selected Measure [Text Block] | PEO and Average Other NEOs Compensation Actually Paid vs. Company-Selected Measure | ||
| Total Shareholder Return Vs Peer Group [Text Block] | PEO and Average Other NEOs Compensation Actually Paid vs. Company and Peer Group TSR | ||
| Tabular List [Table Text Block] | Tabular List of Most Important Financial Performance Measures The following provides a list of the financial performance measures that we believe are the most important financial performance measures used to link NEO compensation to company performance. For more information, see “Executive Compensation — Compensation Discussion and Analysis.” Although we do not in practice use any performance measures to link compensation “actually paid” (as calculated herein) to company performance, we are providing this list in accordance with Item 402(v) of Regulation S-K to provide information on performance measures used by the Compensation Committee to determine NEO compensation, as more fully described in “Executive Compensation — Compensation Discussion and Analysis.” 1. total shareholders’ return; 2. net income; 3. return on average assets; and 4. return on average equity. | ||
| Total Shareholder Return Amount | $ 132.27 | 119.68 | 102.72 |
| Peer Group Total Shareholder Return Amount | 121.59 | 126.83 | 89.52 |
| Net Income (Loss) | $ 300,232,000 | $ 253,922,000 | $ 167,318,000 |
| Company Selected Measure Amount | 12.52 | 11.28 | 7.86 |
| PEO Name | Dennis E. Nixon | ||
| Measure [Axis]: 1 | |||
| Pay vs Performance Disclosure [Table] | |||
| Measure Name | total shareholders’ return | ||
| Measure [Axis]: 2 | |||
| Pay vs Performance Disclosure [Table] | |||
| Measure Name | net income | ||
| Measure [Axis]: 3 | |||
| Pay vs Performance Disclosure [Table] | |||
| Measure Name | return on average assets | ||
| Measure [Axis]: 4 | |||
| Pay vs Performance Disclosure [Table] | |||
| Measure Name | return on average equity | ||
| Non-GAAP Measure Description [Text Block] | (7) The Company has identified return on average common equity (“ROE”), as adjusted for each year indicated as its Company-Selected Measure. Although the Company uses several financial and non-financial performance metrics to evaluate the Company’s performance for purposes of compensation programs, we believe ROE represents the most important financial performance measure that we used to link compensation actually paid to our PEO and non-PEO NEOs for the most recent fiscal year to the Company’s performance. | ||
| Non-PEO NEO [Member] | Option Awards Value In Summary Compensation Table (Grant Date Value) | |||
| Pay vs Performance Disclosure [Table] | |||
| Adjustment to Compensation Amount | $ (150,750) | $ 0 | $ (6,113) |
| Non-PEO NEO [Member] | Total Equity Awards Adjustments [Member] | |||
| Pay vs Performance Disclosure [Table] | |||
| Adjustment to Compensation Amount | 24,572 | 95,203 | 2,338 |
| Non-PEO NEO [Member] | Year-end Fair Value Of Awards Granted In The Current Fiscal Year [Member] | |||
| Pay vs Performance Disclosure [Table] | |||
| Adjustment to Compensation Amount | 141,210 | 0 | 130,099 |
| Non-PEO NEO [Member] | Change In Fair Value Of Outstanding And Unvested Awards Granted In Prior Fiscal Years [Member] | |||
| Pay vs Performance Disclosure [Table] | |||
| Adjustment to Compensation Amount | 35,986 | 32,810 | (51,421) |
| Non-PEO NEO [Member] | Change In Fair Value As Of Vesting Date Of Prior Year Awards Vested During Current Year [Member] | |||
| Pay vs Performance Disclosure [Table] | |||
| Adjustment to Compensation Amount | $ (1,874) | $ 62,393 | $ (70,227) |
