Credit Quality - Additional information (Detail)	3 Months Ended
Mar. 31, 2016 USD ($) Loan	Dec. 31, 2015 USD ($) Loan
Financing Receivable, Allowance for Credit Losses [Line Items]
Restructured loans to borrowers experiencing financial difficulty in excess of	$ 250,000
Performing status returned period	6 months
Covered Loans Recorded as TDR	$ 14,834,000	$ 15,301,000
Waccamaw Bank
Financing Receivable, Allowance for Credit Losses [Line Items]
Percentage of loan and foreclosed real estate losses covered by FDIC	80.00%
Non Covered Loans
Financing Receivable, Allowance for Credit Losses [Line Items]
Accruing loans contractually past due 90 days or more	$ 243,000	0
Covered Loans
Financing Receivable, Allowance for Credit Losses [Line Items]
Covered Loans Recorded as TDR	$ 0	$ 0
PCI loans
Financing Receivable, Allowance for Credit Losses [Line Items]
Number of impaired loans \| Loan	2	2

Loans And Leases Receivable Impaired Number Of Loans

No definition available.

Name:	fcbc_LoansAndLeasesReceivableImpairedNumberOfLoans
Namespace Prefix:	fcbc_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Definition

Percentage of loss covered by FDIC.

+ References

No definition available.

+ Details

Name:	fcbc_PercentageOfLossCoveredByFdic
Namespace Prefix:	fcbc_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Performing status returned period.

+ References

No definition available.

+ Details

Name:	fcbc_PerformingStatusReturnedPeriod
Namespace Prefix:	fcbc_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Restructured loans reserves.

+ References

No definition available.

+ Details

Name:	fcbc_RestructuredLoansReserves
Namespace Prefix:	fcbc_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
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_FinancingReceivableAllowanceForCreditLossesLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

The amount of the outstanding recorded investment related to financing receivables that have been modified by troubled debt restructurings.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 40
-Section 50
-Paragraph 4
-URI http://asc.fasb.org/extlink&oid=25495931&loc=d3e18845-111554

+ Details

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

- Definition

Recorded investment in financing receivables that are 90 days or more past due and still accruing.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 7
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=49124121&loc=d3e5111-111524

+ Details

Name:	us-gaap_FinancingReceivableRecordedInvestment90DaysPastDueAndStillAccruing
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Details

Name:	us-gaap_BusinessAcquisitionAxis=fcbc_WaccamawBankMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	fcbc_ScheduleOfFinancingReceivableAgingAxis=fcbc_NonCoveredLoansMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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

- Details

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