BORROWING ARRANGEMENTS, Lines of Credit (Details) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022
Line of Credit Facility [Abstract]
Carrying amount of FHLB stock	$ 3.0	$ 2.8
FHLB stock, available borrowing capacity	1,100.0	920.2
Outstanding borrowings	0.0	0.0
Bank Subsidiary [Member] \| Federal Reserve Bank of Dallas (FRB) [Member]
Line of Credit Facility [Abstract]
Line of credit, current borrowing capacity	595.4	648.3
Bank Subsidiary [Member] \| Federal Reserve Bank of Dallas (FRB) [Member] \| Bank Term Funding Program [Member]
Line of Credit Facility [Abstract]
Line of credit, securities available to be used as collateral for additional borrowings	134.0
Bank Subsidiary [Member] \| Multiple Banks [Member]
Line of Credit Facility [Abstract]
Line of credit, current borrowing capacity	$ 140.0	$ 160.0

Amount of securities available to be used as a collateral for additional borrowings under the credit facility.

No definition available.

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Balance Type:	credit
Period Type:	instant

- Definition

Amount of advances or credit lines available from the Federal Home Loan Bank (FHLB).

+ References

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-Topic 942
-SubTopic 210
-Name Accounting Standards Codification
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- Definition

Federal Home Loan Bank (FHLB) stock represents an equity interest in a FHLB. It does not have a readily determinable fair value because its ownership is restricted and it lacks a market (liquidity).

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Topic 942
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- Definition

The carrying value as of the balance sheet date of the current and noncurrent portions of long-term obligations drawn from a line of credit, which is a bank's commitment to make loans up to a specific amount. Examples of items that might be included in the application of this element may consist of letters of credit, standby letters of credit, and revolving credit arrangements, under which borrowings can be made up to a maximum amount as of any point in time conditional on satisfaction of specified terms before, as of and after the date of drawdowns on the line. Includes short-term obligations that would normally be classified as current liabilities but for which (a) postbalance sheet date issuance of a long term obligation to refinance the short term obligation on a long term basis, or (b) the enterprise has entered into a financing agreement that clearly permits the enterprise to refinance the short-term obligation on a long term basis and the following conditions are met (1) the agreement does not expire within 1 year and is not cancelable by the lender except for violation of an objectively determinable provision, (2) no violation exists at the BS date, and (3) the lender has entered into the financing agreement is expected to be financially capable of honoring the agreement.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
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Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
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+ Details

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Namespace Prefix:	us-gaap_
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Balance Type:	credit
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- References

No definition available.

+ Details

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- Definition

Amount of current borrowing capacity under the credit facility considering any current restrictions on the amount that could be borrowed (for example, borrowings may be limited by the amount of current assets), but without considering any amounts currently outstanding under the facility.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
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-Section S99
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- Details

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- Details

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- Details

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