INVESTMENT SECURITIES - Summary of Investments in Debt and Equity Securities Reported in the Financial Statements at an Amount Less Than Their Historical Cost (Details) - Investments reported at less than historical cost - USD ($) $ in Thousands	Sep. 30, 2026	Dec. 31, 2025
Schedule of Investments [Line Items]
Historical cost	$ 1,538,933	$ 1,436,638
Fair value	1,248,181	1,267,891
Gross unrealized losses	$ (290,752)	$ (168,747)
Percentage of the Corporation's investment securities available for sale in an unrealized loss position	99.70%	90.10%

INVESTMENT SECURITIES - Summary of Investments in Debt and Equity Securities Reported in the Financial Statements at an Amount Less Than Their Historical Cost (Details) - Investments reported at less than historical cost - USD ($)
$ in Thousands

Sep. 30, 2026

Dec. 31, 2025

Schedule of Investments [Line Items]

Historical cost

$ 1,538,933

$ 1,436,638

Fair value

1,248,181

1,267,891

Gross unrealized losses

$ (290,752)

$ (168,747)

Percentage of the Corporation's investment securities available for sale in an unrealized loss position

99.70%

90.10%

- Definition

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.

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+ Details