Name:	fcbc_AvailableForSaleSecuritiesGrossUnrealizedGainAccumulatedInInvestments
Namespace Prefix:	fcbc_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

Amount of accumulated pre-tax unrealized loss before deducting pre-tax unrealized gain on investments in available-for-sale securities impacting investments.

No definition available.

Name:	fcbc_AvailableForSaleSecuritiesGrossUnrealizedLossAccumulatedInInvestments
Namespace Prefix:	fcbc_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

Municipal Bonds Portfolio Carrying Value Percentage

No definition available.

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

Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 25
-Paragraph 1
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=51813488&loc=d3e22054-111558

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 5
-Subparagraph (aa)
-URI http://asc.fasb.org/extlink&oid=27724398&loc=d3e27232-111563

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=49167202&loc=d3e26610-111562

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

This item represents the cost of debt and equity securities, which are categorized neither as held-to-maturity nor trading, net of adjustments including accretion, amortization, collection of cash, previous other-than-temporary impairments recognized in earnings (less any cumulative-effect adjustments recognized, as defined), and fair value hedge accounting adjustments, if any.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.2)
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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

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.

No definition available.

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

Name:	fcbc_ScheduleOfAvailableForSaleAndHeldToMaturitySecuritiesMajorTypesOfSecuritiesAxis=fcbc_StateAndMunicipalSecuritiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis=stpr_NY
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis=stpr_MN
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis=stpr_NJ
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis=stpr_CT
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis=stpr_WI
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis=stpr_OH
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis=stpr_MA
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis=stpr_TX
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis=stpr_IA
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: