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Summary of Significant Accounting Policies - SBA Loans (Details) | 12 Months Ended
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Dec. 31, 2021
Accounting Policies [Abstract] |
SBA loan, amortization period | 25 years

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- Definition SBA Loan, Amortization Period + References No definition available. + Details
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Namespace Prefix: | fbnc_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

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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