BASIS OF PRESENTATION AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Textual) (Details) (USD $)	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013
Noncontrolling Interest [Line Items]
Interest-bearing deposits in banks and other financial institutions	$ 105,053,000us-gaap_InterestBearingDepositsInBanks	$ 98,066,000us-gaap_InterestBearingDepositsInBanks
Required daily cash and cash equivalents reserve balance	10,000,000fbspra_CashReserveRequired	11,500,000fbspra_CashReserveRequired
Federal Reserve stock, investment requirement as a percent of First Bank capital stock and capital surplus	6.00%
Federal Home Loan Bank of Des Moines [Member]
Noncontrolling Interest [Line Items]
Federal Home Loan Bank stock, investment requirement as a percent of First Bank total Assets	0.12%
Federal Home Loan Bank stock, investment requirement, maximum amount	10,000,000
Federal Home Loan Bank stock, investment requirement, maximum, percent of advances	4.45%
Federal Home Loan Bank stock	7,000,000	7,800,000
Federal Reserve Bank of St. Louis [Member]
Noncontrolling Interest [Line Items]
Federal Reserve Bank stock	$ 23,400,000	$ 19,600,000
First Capital America, Inc. [Member]
Noncontrolling Interest [Line Items]
Noncontrolling Interest, Ownership Percentage by Parent	46.77%
First Bank [Member]
Noncontrolling Interest [Line Items]
Noncontrolling Interest, Ownership Percentage by Parent	53.23%
Buildings and improvements [Member] \| Minimum [Member]
Noncontrolling Interest [Line Items]
Property, plant and equipment, useful life	5 years
Buildings and improvements [Member] \| Maximum [Member]
Noncontrolling Interest [Line Items]
Property, plant and equipment, useful life	40 years
Equipment [Member] \| Minimum [Member]
Noncontrolling Interest [Line Items]
Property, plant and equipment, useful life	3 years
Equipment [Member] \| Maximum [Member]
Noncontrolling Interest [Line Items]
Property, plant and equipment, useful life	7 years

Required Daily Cash and Cash Equivalents Reserve Balance

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- Definition

Federal Home Loan Bank Stock, Investment Requirement as a Percent of First Bank Total Assets

+ References

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- Definition

Federal Home Loan Bank Stock, Investment Requirement, Maximum Amount

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- Definition

Federal Home Loan Bank Stock, Investment Requirement, Maximum, Percent of Advances

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- Definition

Federal Reserve Bank Stock, Investment Requirement as a Percent of First Bank Capital Stock and Capital Surplus

+ References

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- Definition

Federal Home Loan Bank (FHLB) stock represents an equity interest in a FHLB. It does not have a readily determinable fair value because its ownership is restricted and it lacks a market (liquidity).

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 942

-SubTopic 325

-Section 45

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=6478792&loc=d3e63345-112809

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- Definition

Federal Reserve Bank stock represents an equity interest in the Federal Reserve Bank. It does not have a readily determinable fair value because its ownership is restricted and it lacks a market (liquidity).

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- Definition

For banks and other depository institutions (including Federal Reserve Banks, if applicable): Interest-bearing deposits in other financial institutions for relatively short periods of time including, for example, certificates of deposits, which are presented separately from cash on the balance sheet.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 942

-SubTopic 210

-Section 45

-Paragraph 4

-URI http://asc.fasb.org/extlink&oid=6476743&loc=d3e59706-112781

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 03

-Paragraph 2

-Article 9

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 942

-SubTopic 210

-Section S99

-Paragraph 1

-Subparagraph (SX 210.9-03.2)

-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

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The parent entity's interest in net assets of the subsidiary, expressed as a percentage.

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Useful life of long lived, physical assets used in the normal conduct of business and not intended for resale, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. Examples include, but not limited to, land, buildings, machinery and equipment, office equipment, furniture and fixtures, and computer equipment.

+ References

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