Deposits - Additional Information About Corporation's Deposits (Detail) - USD ($) $ in Thousands	Sep. 30, 2026	Dec. 31, 2025
Deposit Liability [Line Items]
Deposits from foreign sources (primarily Mexico)	$ 1,310,776	$ 1,265,896
Non-interest-bearing public funds deposits	14,546,225	14,143,815
Interest-bearing public funds deposits	29,676,146	28,774,049
Total deposits that are not covered by deposit insurance	23,485,329	22,286,545
Time deposits that are not covered by deposit insurance	3,215,443	2,877,253
Public Funds [Member]
Deposit Liability [Line Items]
Non-interest-bearing public funds deposits	427,857	662,354
Interest-bearing public funds deposits	$ 544,547	$ 768,726

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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Reference 2: http://www.xbrl.org/2003/role/disclosureRef
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Reference 3: http://www.xbrl.org/2003/role/disclosureRef
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Reference 4: http://www.xbrl.org/2003/role/disclosureRef
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Reference 5: http://www.xbrl.org/2003/role/disclosureRef
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Reference 6: http://www.xbrl.org/2003/role/disclosureRef
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Amount of uninsured deposit liability.

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The aggregate of all foreign interest-bearing and noninterest-bearing deposit liabilities.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Topic 942
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The aggregate of all domestic and foreign interest-bearing deposit liabilities.

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The aggregate amount of all domestic and foreign noninterest-bearing deposits liabilities held by the entity.

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Amount of uninsured time deposit liability in excess of Federal Deposit Insurance Corporation (FDIC) insurance limit or similar state deposit insurance regime in United States of America (US). Excludes time deposit that is otherwise uninsured.

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