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SIGNIFICANT ACCOUNTING POLICIES - Securities (Details) $ in Millions | Dec. 31, 2024 USD ($)
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Accounting Policies [Abstract] |
Debt securities, accrued interest | $ 10.5

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- Definition Debt Securities, Accrued Interest + References No definition available. + Details
Name: | buse_DebtSecuritiesAccruedInterest
Namespace Prefix: | buse_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

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- References No definition available. + Details
Name: | us-gaap_AccountingPoliciesAbstract
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration