Financing Receivable, Excluding Accrued Interest, Advances

No definition available.

Name:	fbnc_FinancingReceivableExcludingAccruedInterestAdvances
Namespace Prefix:	fbnc_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Financing Receivable, Excluding Accrued Interest, Available Credit

+ References

No definition available.

+ Details

Name:	fbnc_FinancingReceivableExcludingAccruedInterestAvailableCredit
Namespace Prefix:	fbnc_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Financing Receivable, Nonaccrual, Write-Off, Threshold Percentage

+ References

No definition available.

+ Details

Name:	fbnc_FinancingReceivableNonaccrualWriteOffThresholdPercentage
Namespace Prefix:	fbnc_
Data Type:	dtr-types1:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Financing Receivable, Number of New Loans

+ References

No definition available.

+ Details

Name:	fbnc_FinancingReceivableNumberOfNewLoans
Namespace Prefix:	fbnc_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

Individually Evaluated Loans, Collateral Dependent, Nonaccrual And Accruing, Net Book Balance, Evaluation Threshold, Amount

+ References

No definition available.

+ Details

Name:	fbnc_IndividuallyEvaluatedLoansCollateralDependentNonaccrualAndAccruingNetBookBalanceEvaluationThresholdAmount
Namespace Prefix:	fbnc_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Individually Evaluated Loans, Nonaccrual, Net Book Balance, Evaluation Threshold, Amount

+ References

No definition available.

+ Details

Name:	fbnc_IndividuallyEvaluatedLoansNonaccrualNetBookBalanceEvaluationThresholdAmount
Namespace Prefix:	fbnc_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Number Of Loans To Debtors With Nonperforming Loans

+ References

No definition available.

+ Details

Name:	fbnc_NumberOfLoansToDebtorsWithNonperformingLoans
Namespace Prefix:	fbnc_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Definition

For an entity that discloses a concentration risk in relation to quantitative amount, which serves as the "benchmark" (or denominator) in the equation, this concept represents the concentration percentage derived from the division.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 42
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482810/280-10-50-42

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 50
-Paragraph 21
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482907/825-10-50-21

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 50
-Paragraph 20
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482907/825-10-50-20

Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Topic 275
-SubTopic 10
-Section 50
-Paragraph 18
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482861/275-10-50-18

Reference 5: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Topic 275
-SubTopic 10
-Section 50
-Paragraph 20
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482861/275-10-50-20

+ Details

Name:	us-gaap_ConcentrationRiskPercentage1
Namespace Prefix:	us-gaap_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount excluding accrued interest, of allowance for credit loss on financing receivable. Excludes net investment in lease.

+ References

+ Details

Name:	us-gaap_FinancingReceivableAllowanceForCreditLossExcludingAccruedInterest
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amortized cost excluding accrued interest, before allowance for credit loss, of financing receivable. Excludes net investment in lease.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 326
-SubTopic 20
-Name Accounting Standards Codification
-Section 45
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147479344/326-20-45-1

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 326
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 3B
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147479319/326-20-50-3B

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 326
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 5
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147479319/326-20-50-5

+ Details

Name:	us-gaap_FinancingReceivableExcludingAccruedInterestBeforeAllowanceForCreditLoss
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount of interest income on financing receivable on nonaccrual status.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 326
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 16
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147479319/326-20-50-16

+ Details

Name:	us-gaap_FinancingReceivableNonaccrualInterestIncome
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Amount of unamortized purchase premium (discount) on financing receivable. Excludes financing receivable covered under loss sharing agreement.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 310
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 4
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481962/310-10-50-4

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 310
-SubTopic 20
-Name Accounting Standards Codification
-Section 45
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481598/310-20-45-1

+ Details

Name:	us-gaap_FinancingReceivableUnamortizedPurchasePremiumDiscount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- 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.

+ References

No definition available.

+ Details

Name:	us-gaap_LoansAndLeasesReceivableDisclosureLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Recorded investment of consumer mortgage loan receivables secured by residential real estate properties for which formal foreclosure proceedings are in process.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Section 50
-Paragraph 35
-SubTopic 10
-Topic 310
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481962/310-10-50-35

+ Details

Name:	us-gaap_MortgageLoansInProcessOfForeclosureAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

The cash inflow associated with collection, whether partial or full, of long-term loans to a related party. Alternate caption: Proceeds from Advances to Affiliates.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 850
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147483326/850-10-50-1

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 230
-SubTopic 10
-Name Accounting Standards Codification
-Section 45
-Paragraph 12
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482740/230-10-45-12

+ Details

Name:	us-gaap_ProceedsFromCollectionOfLongtermLoansToRelatedParties
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Details

Name:	us-gaap_PledgedStatusAxis=us-gaap_AssetPledgedAsCollateralMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivablePortfolioSegmentAxis=us-gaap_ConsumerPortfolioSegmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivablePortfolioSegmentAxis=us-gaap_CommercialPortfolioSegmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_CollateralAxis=sic_Z6500
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_ConcentrationRiskByBenchmarkAxis=fbnc_ReceivableBenchmarkMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_ConcentrationRiskByTypeAxis=fbnc_CollateralTypeConcentrationRiskMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_CollateralAxis=srt_HotelMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_RangeAxis=srt_MinimumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_RangeAxis=srt_MaximumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_CollateralAxis=fbnc_NonRealEstateMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RelatedPartyTransactionsByRelatedPartyAxis=fbnc_OfficersAndDirectorsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancialInstrumentAxis=us-gaap_UnusedLinesOfCreditMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=us-gaap_FixedRateResidentialMortgageMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=us-gaap_UnfundedLoanCommitmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis=fbnc_SmallBusinessAdministrationLoansMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Loans, Allowance for Credit Losses, and Asset Quality Information - Narrative (Details)	3 Months Ended
	Mar. 31, 2024 USD ($) loan	Mar. 31, 2023 USD ($)	Dec. 31, 2023 USD ($) loan	Dec. 31, 2022 USD ($)
Loans and Leases Receivable Disclosure [Line Items]
Unamortized premium (discount) on acquired loans	$ (21,600,000)		$ (24,000,000)
Total loans, net of deferred loan fees	$ 8,076,506,000		$ 8,150,102,000
Number of loans to debtors with nonperforming loans \| loan	1		1
Interest income on nonaccrual loans	$ 0	$ 0
Non accrual individually evaluated loan threshold	500,000
Collateral dependent individually evaluated loan threshold	500,000
Allowance for credit losses on loans	110,067,000	106,396,000	$ 109,853,000	$ 90,967,000
Asset Pledged as Collateral
Loans and Leases Receivable Disclosure [Line Items]
Total loans, net of deferred loan fees	6,500,000,000		6,500,000,000
Consumer loans
Loans and Leases Receivable Disclosure [Line Items]
Allowance for credit losses on loans	3,113,000	3,295,000	2,992,000	2,900,000
Commercial and industrial
Loans and Leases Receivable Disclosure [Line Items]
Allowance for credit losses on loans	$ 20,294,000	23,073,000	21,227,000	17,718,000
Real Estate
Loans and Leases Receivable Disclosure [Line Items]
Threshold percentage to write-off nonaccrual loans	90.00%
Real Estate \| Receivable Benchmark \| Collateral Type Concentration Risk
Loans and Leases Receivable Disclosure [Line Items]
Concentration risk percentage	88.00%
Hotel \| Minimum
Loans and Leases Receivable Disclosure [Line Items]
Threshold percentage to write-off nonaccrual loans	10.00%
Hotel \| Maximum
Loans and Leases Receivable Disclosure [Line Items]
Threshold percentage to write-off nonaccrual loans	25.00%
Non Real Estate
Loans and Leases Receivable Disclosure [Line Items]
Threshold percentage to write-off nonaccrual loans	75.00%
Officers and Directors
Loans and Leases Receivable Disclosure [Line Items]
Total loans, net of deferred loan fees	$ 64,600,000		63,700,000
Number of new loans \| loan	0
Financing receivable, excluding accrued interest, advances	$ 1,400,000
Repayments received from related parties	500,000
Officers and Directors \| Unused lines of Credit
Loans and Leases Receivable Disclosure [Line Items]
Financing receivable, excluding accrued interest, available credit	1,200,000		2,700,000
Residential Mortgage Loans
Loans and Leases Receivable Disclosure [Line Items]
Presold mortgages in process of settlement	1,600,000		1,000,000
Unfunded Loan Commitment
Loans and Leases Receivable Disclosure [Line Items]
Allowance for credit losses on loans	10,768,000	$ 14,357,000	11,369,000	$ 13,306,000
SBA Loans
Loans and Leases Receivable Disclosure [Line Items]
Unamortized premium (discount) on acquired loans	$ (3,400,000)		$ (3,500,000)