Note 13 - Stock-Based Compensation (Details) - Nonvested Option Shares and Changes (USD $)	3 Months Ended
Mar. 31, 2015	Mar. 31, 2014
Nonvested Option Shares and Changes [Abstract]
Nonvested	62,700	58,750
Nonvested	$ 6.14	$ 5.38
Granted	14,000	18,000
Granted	$ 8.01	$ 8.36
Forfeited	(600)	(2,250)
Forfeited	$ 6.52	$ 6.52
Vested	(11,000)	(7,000)
Vested	$ 5.47	$ 5.40
Nonvested	65,100	67,500
Nonvested	$ 6.65	$ 6.14

Name:	fsbk_NonvestedOptionSharesAndChangesAbstract
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Gross number of share options (or share units) granted during the period.

+ References

No definition available.

+ Details

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- Definition

The weighted average grant-date fair value of options granted during the reporting period as calculated by applying the disclosed option pricing methodology.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (d)(1)

-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

+ Details

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- Definition

Number of non-vested options outstanding.

+ References

No definition available.

+ Details

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- Definition

Number of non-vested options forfeited.

+ References

No definition available.

+ Details

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- Definition

Weighted average grant-date fair value of non-vested options forfeited.

+ References

No definition available.

+ Details

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- Definition

Weighted average grant-date fair value of non-vested options outstanding.

+ References

No definition available.

+ Details

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- Definition

Number of options vested.

+ References

No definition available.

+ Details

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- Definition

Weighted average grant-date fair value of options vested.

+ References

No definition available.

+ Details

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