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Regulatory Restrictions - Narrative (Details) $ in Millions | Dec. 31, 2024 USD ($)
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Regulatory Restrictions [Abstract] |
Restricted investment in bank | $ 1,100
Average reserve balance | $ 0

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- Definition Regulatory Restrictions + References No definition available. + Details
Name: | fbnc_RegulatoryRestrictionsAbstract
Namespace Prefix: | fbnc_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

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- Definition The amount of restricted investment in bank as to transfer to the company without obtaining prior regulatory approval. + References No definition available. + Details
Name: | fbnc_RestrictedInvestmentInBank
Namespace Prefix: | fbnc_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

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- Definition Amount of cash subject to withdrawal restrictions, restricted deposits held as compensating balances, and cash and securities segregated in compliance with regulations (such as cash deposited in a special reserve account for the exclusive benefit of customers). + References No definition available. + Details
Name: | us-gaap_CashAndSecuritiesSegregatedUnderFederalAndOtherRegulations
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant