Loans, Allowance for Credit Losses, and Asset Quality Information - Schedule of Activity in Allowance for Loan Losses for Loans (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended	12 Months Ended
Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021	Dec. 31, 2021
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	$ 82,181	$ 65,022	$ 78,789	$ 52,388	$ 52,388
Allowance for acquired PCD loans					4,895
Charge-offs	(1,205)	(1,105)	(4,008)	(5,553)	(7,602)
Recoveries	511	1,111	3,206	3,618	4,922
Provisions/(Reversals)	5,100	(1,400)	8,600	(1,400)	9,611
Ending balance	86,587	63,628	86,587	63,628	78,789
Cumulative Effect, Period Of Adoption, Adjustment
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance				14,575	14,575
Commercial, financial, and agricultural
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	15,450	14,809	16,249	11,316	11,316
Allowance for acquired PCD loans					2,917
Charge-offs	(512)	(899)	(2,030)	(2,887)	(3,722)
Recoveries	166	398	636	1,065	1,744
Provisions/(Reversals)	2,482	(808)	2,731	939	927
Ending balance	17,586	13,500	17,586	13,500	16,249
Commercial, financial, and agricultural \| Cumulative Effect, Period Of Adoption, Adjustment
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance				3,067	3,067
Real estate, commercial \| Real estate – construction, land development & other land loans
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	16,171	10,104	16,519	5,355	5,355
Allowance for acquired PCD loans					165
Charge-offs	0	0	0	(66)	(245)
Recoveries	109	98	376	784	948
Provisions/(Reversals)	(1,352)	2,187	(1,967)	176	4,156
Ending balance	14,928	12,389	14,928	12,389	16,519
Real estate, commercial \| Real estate – construction, land development & other land loans \| Cumulative Effect, Period Of Adoption, Adjustment
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance				6,140	6,140
Real estate, commercial \| Real estate – mortgage – commercial and other
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	37,194	25,358	30,342	23,603	23,603
Allowance for acquired PCD loans					1,489
Charge-offs	(470)	(4)	(1,333)	(1,838)	(2,295)
Recoveries	112	79	1,567	419	533
Provisions/(Reversals)	938	(1,336)	7,198	2,170	7,269
Ending balance	37,774	24,097	37,774	24,097	30,342
Real estate, commercial \| Real estate – mortgage – commercial and other \| Cumulative Effect, Period Of Adoption, Adjustment
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance				(257)	(257)
Real estate, mortgage \| Real estate – mortgage – residential (1-4 family) first mortgages
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	8,650	8,651	8,686	8,048	8,048
Allowance for acquired PCD loans					222
Charge-offs	0	(24)	0	(138)	(273)
Recoveries	1	176	16	499	761
Provisions/(Reversals)	2,064	(1,032)	2,013	(3,222)	(2,656)
Ending balance	10,715	7,771	10,715	7,771	8,686
Real estate, mortgage \| Real estate – mortgage – residential (1-4 family) first mortgages \| Cumulative Effect, Period Of Adoption, Adjustment
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance				2,584	2,584
Real estate, mortgage \| Real estate – mortgage – home equity loans / lines of credit
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	2,086	3,737	4,337	2,375	2,375
Allowance for acquired PCD loans					92
Charge-offs	(2)	0	(43)	(139)	(400)
Recoveries	85	311	446	540	578
Provisions/(Reversals)	597	(546)	(1,974)	(1,854)	(888)
Ending balance	2,766	3,502	2,766	3,502	4,337
Real estate, mortgage \| Real estate – mortgage – home equity loans / lines of credit \| Cumulative Effect, Period Of Adoption, Adjustment
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance				2,580	2,580
Consumer loans
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	2,630	2,363	2,656	1,478	1,478
Allowance for acquired PCD loans					10
Charge-offs	(221)	(178)	(602)	(485)	(667)
Recoveries	38	49	165	311	358
Provisions/(Reversals)	371	135	599	391	803
Ending balance	2,818	2,369	2,818	2,369	2,656
Consumer loans \| Cumulative Effect, Period Of Adoption, Adjustment
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance				674	674
Unallocated
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	0	0	0	213	213
Allowance for acquired PCD loans					0
Charge-offs	0	0	0	0	0
Recoveries	0	0	0	0	0
Provisions/(Reversals)	0	0	0	0	0
Ending balance	$ 0	$ 0	$ 0	0	0
Unallocated \| Cumulative Effect, Period Of Adoption, Adjustment
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance				$ (213)	$ (213)

Financing Receivable, Excluding Accrued Interest, Allowance For Credit Loss, Increase From Acquisition

No definition available.

Name:	fbnc_FinancingReceivableExcludingAccruedInterestAllowanceForCreditLossIncreaseFromAcquisition
Namespace Prefix:	fbnc_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

+ References

No definition available.

+ Details

Name:	us-gaap_AllowanceForDoubtfulAccountsReceivableRollforward
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
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

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 20
-Section 45
-Paragraph 1
-URI https://asc.fasb.org/extlink&oid=124255206&loc=SL82895884-210446

+ Details

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

- Definition

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

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 20
-Section 50
-Paragraph 13
-Subparagraph (e)
-URI https://asc.fasb.org/extlink&oid=124255953&loc=SL82919249-210447

+ Details

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

- Definition

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

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 20
-Section 50
-Paragraph 13
-Subparagraph (d)
-URI https://asc.fasb.org/extlink&oid=124255953&loc=SL82919249-210447

+ Details

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

- Definition

Amount, excluding accrued interest, of credit loss expense (reversal of expense) on financing receivable. Excludes net investment in lease.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 20
-Section 50
-Paragraph 13
-Subparagraph (b)
-URI https://asc.fasb.org/extlink&oid=124255953&loc=SL82919249-210447

+ Details

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

- Details

Name:	srt_CumulativeEffectPeriodOfAdoptionAxis=srt_CumulativeEffectPeriodOfAdoptionAdjustmentMember
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_FinancingReceivablePortfolioSegmentAxis=us-gaap_CommercialRealEstatePortfolioSegmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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

- Details

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

- Details

Name:	us-gaap_FinancingReceivablePortfolioSegmentAxis=us-gaap_ResidentialPortfolioSegmentMember
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_HomeEquityLoanMember
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_UnallocatedFinancingReceivablesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: