Derivative Instruments and Hedging Activities, Derivative Contract Type (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended	12 Months Ended
Mar. 31, 2015	Dec. 31, 2014
Interest Rate Swap [Member] \| Cash Flow Hedging [Member]
Derivatives in cash flow hedging relationships [Abstract]
Amount of gain (loss) recognized in OCI on derivatives, net of tax (effective portion)	$ (31)	$ (53)
Amount of gain (loss) recognized in income on derivative (ineffective portion)	0	0
Interest Rate Swap [Member] \| Fair Value Hedging [Member] \| Interest Income [Member]
Derivatives in fair value hedging relationships [Abstract]
Gain or (Loss) on swaps	(12)	(58)
Interest Rate Swap-10 Year Cash Flow [Member]
Derivatives, Fair Value [Line Items]
Expiration date	Sep. 15, 2020	Sep. 15, 2020
Interest Rate Swap-10 Year Cash Flow [Member] \| Other Liabilities [Member]
Derivatives, Fair Value [Line Items]
Notional/ contract amount	4,000	4,000
Estimated net fair value	(351)	(304)
Interest Rate Swap-10 Year Fair Value 1 [Member]
Derivatives, Fair Value [Line Items]
Expiration date	Aug. 15, 2021	Aug. 15, 2021
Interest Rate Swap-10 Year Fair Value 1 [Member] \| Other Assets [Member]
Derivatives, Fair Value [Line Items]
Notional/ contract amount		2,114
Estimated net fair value		(66)
Interest Rate Swap-10 Year Fair Value 1 [Member] \| Other Liabilities [Member]
Derivatives, Fair Value [Line Items]
Notional/ contract amount	2,102
Estimated net fair value	(96)
Interest Rate Swap-10 Year Fair Value 2 [Member]
Derivatives, Fair Value [Line Items]
Expiration date	Aug. 15, 2021	Aug. 15, 2021
Interest Rate Swap-10 Year Fair Value 2 [Member] \| Other Assets [Member]
Derivatives, Fair Value [Line Items]
Notional/ contract amount		1,993
Estimated net fair value		(63)
Interest Rate Swap-10 Year Fair Value 2 [Member] \| Other Liabilities [Member]
Derivatives, Fair Value [Line Items]
Notional/ contract amount	1,982
Estimated net fair value	(92)
Interest Rate Swap-10 Year Fair Value 3 [Member]
Derivatives, Fair Value [Line Items]
Expiration date	Sep. 26, 2022	Sep. 26, 2022
Interest Rate Swap-10 Year Fair Value 3 [Member] \| Other Assets [Member]
Derivatives, Fair Value [Line Items]
Notional/ contract amount		1,000
Estimated net fair value		16
Interest Rate Swap-10 Year Fair Value 3 [Member] \| Other Liabilities [Member]
Derivatives, Fair Value [Line Items]
Notional/ contract amount	993
Estimated net fair value	(2)
Interest Rate Swap-10 Yr Fair Value 4 [Member]
Derivatives, Fair Value [Line Items]
Expiration date	Feb. 12, 2022
Interest Rate Swap-10 Yr Fair Value 4 [Member] \| Other Liabilities [Member]
Derivatives, Fair Value [Line Items]
Notional/ contract amount	4,800
Estimated net fair value	$ (66)

Aggregate notional amount specified by the derivative(s). Expressed as an absolute value.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Article 12

-Section 13

-Sentence Column B

+ Details

Name:	invest_DerivativeNotionalAmount
Namespace Prefix:	invest_
Data Type:	xbrli:monetaryItemType
Balance Type:	na
Period Type:	instant

- Definition

Fair value of the assets less the liabilities of a derivative or group of derivatives.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 825

-SubTopic 10

-Section 50

-Paragraph 10

-Subparagraph (a)

-URI http://asc.fasb.org/extlink&oid=35750535&loc=d3e13433-108611

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 815

-SubTopic 10

-Section 45

-Paragraph 5

-URI http://asc.fasb.org/extlink&oid=6945355&loc=d3e41228-113958

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 825

-SubTopic 10

-Section 50

-Paragraph 15

-URI http://asc.fasb.org/extlink&oid=35750535&loc=d3e13495-108611

Reference 4: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 815

-SubTopic 10

-Section 45

-Paragraph 6

-URI http://asc.fasb.org/extlink&oid=6945355&loc=d3e41271-113958

+ Details

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

- Details

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

- Definition

The portion of gains and losses (net) on derivative instruments designated and qualifying as hedging instruments representing (a) the amount of the hedge ineffectiveness and (b) the amount, if any, excluded from the assessment of hedge effectiveness.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 815

-SubTopic 10

-Section 50

-Paragraph 4C

-Subparagraph (d)

-URI http://asc.fasb.org/extlink&oid=35706170&loc=SL5624171-113959

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 815

-SubTopic 25

-Section 50

-Paragraph 1

-Subparagraph (a)(1),(2)

-URI http://asc.fasb.org/extlink&oid=6886632&loc=d3e76258-113986

+ Details

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

- Definition

The effective portion of loss reclassified from accumulated other comprehensive income into income on derivative instruments designated and qualifying as hedging instruments.

+ References

+ Details

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

- Definition

Date the derivative contract matures, in CCYY-MM-DD format.

+ References

No definition available.

+ Details

Name:	us-gaap_DerivativeMaturityDates
Namespace Prefix:	us-gaap_
Data Type:	xbrli:dateItemType
Balance Type:	na
Period Type:	duration

- Details

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

- Definition

Total amount of gain (loss) derived from fair value hedges recognized in earnings in the period.

+ References

+ Details

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

- Details

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

- Details

Name:	us-gaap_DerivativeInstrumentRiskAxis=fbss_InterestRateSwapFiveMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DerivativeInstrumentRiskAxis=fbss_InterestRateSwapFourMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DerivativeInstrumentRiskAxis=fbss_InterestRateSwapOneMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DerivativeInstrumentRiskAxis=fbss_InterestRateSwapThreeMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DerivativeInstrumentRiskAxis=fbss_InterestRateSwapTwoMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DerivativeInstrumentRiskAxis=us-gaap_InterestRateSwapMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: