Company-Obligated Mandatorily Redeemable Capital Securities (Details) (USD $)	3 Months Ended
Sep. 30, 2013	Sep. 21, 2006
Floating Rate Junior Subordinated Deferrable Interest Debentures [Member]
Debt Instrument [Line Items]
Principal amount of debt	$ 4,000,000
Maturity date	Dec. 31, 2036
Floating Rate Capital Securities [Member]
Class of Stock [Line Items]
Face amount of capital securities		4,000,000
Capital securities, basis spread on variable rate (in hundredths)	2.00%
Capital securities, description of variable rate basis	three month LIBOR
Capital securities	$ 4,124,000
Callable period of capital securities	5 years

The carrying amount of capital securities as of the balance sheet date.

No definition available.

Name:	fbss_CapitalSecurities
Namespace Prefix:	fbss_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The percentage points added to the reference rate to compute the variable rate on the capital securities.

+ References

No definition available.

+ Details

Name:	fbss_CapitalSecuritiesBasisSpreadOnVariableRate
Namespace Prefix:	fbss_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

The period after issue date, over which the issuer of the capital security is permitted to repay or convert it before the stated maturity date (early retirement date).

+ References

No definition available.

+ Details

Name:	fbss_CapitalSecuritiesCallablePeriod
Namespace Prefix:	fbss_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

The reference rate for the variable rate of the capital securities, such as LIBOR or the US Treasury rate and the maturity of the reference rate used, such as three months or six months LIBOR.

+ References

No definition available.

+ Details

Name:	fbss_CapitalSecuritiesDescriptionOfVariableRateBasis
Namespace Prefix:	fbss_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Face amount of capital securities issued.

+ References

No definition available.

+ Details

Name:	fbss_CapitalSecuritiesFaceAmount
Namespace Prefix:	fbss_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Details

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

- Definition

The stated principal amount of the debt instrument at time of issuance, which may vary from the carrying amount because of unamortized premium or discount.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 835

-SubTopic 30

-Section 45

-Paragraph 2

-URI http://asc.fasb.org/extlink&oid=6451184&loc=d3e28551-108399

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 835

-SubTopic 30

-Section 55

-Paragraph 8

-URI http://asc.fasb.org/extlink&oid=6584090&loc=d3e28878-108400

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

-Publisher AICPA

-Name Accounting Principles Board Opinion (APB)

-Number 21

-Paragraph 16, 20

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

+ Details

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

- Details

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

- Definition

Date when the debt instrument is scheduled to be fully repaid, in CCYY-MM-DD format.

+ References

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 22

-Article 5

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.22(a)(2))

-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 129

-Paragraph 2, 4

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

+ Details

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