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Short-Term Borrowings (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2020	Dec. 31, 2019
Short-Term Borrowings (Details) [Line Items]
Federal funds lines	$ 41.0	$ 41.0
Retail Repurchase Agreements [Member]
Short-Term Borrowings (Details) [Line Items]
Mortgage-backed securities maturity, basis of allocation description	These securities have various maturity dates from 2022 through 2044.
Secured by agency securities with corresponding liabilities	$ 10.8
Secured by mortgage-backed securities with corresponding liabilities	$ 14.1
Short-term borrowings mature term, description	The repurchase agreements mature within one month.

X

- Definition

This item represents disclosure of the basis (methodology and assumptions) for allocating securities which do not have a single contractual maturity date, such as mortgage-backed securities, over several maturity groupings. Such securities are categorized as held-to-maturity.

+ References

No definition available.

+ Details

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X

- Definition

Secured by agency securities with corresponding liabilities.

+ References

No definition available.

+ Details

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Namespace Prefix:	sbfg_
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X

- Definition

Secured by mortgage-backed securities with corresponding liabilities.

+ References

No definition available.

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- References

No definition available.

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- Definition

Description of the maturity date of the debt instrument including whether the debt matures serially and, if so, a brief description of the serial maturities.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-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=120391452&loc=d3e13212-122682

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X

- Definition

Amount of short term borrowing where a bank borrows, at the federal funds rate, from another bank.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03.13(1))
-URI http://asc.fasb.org/extlink&oid=120398452&loc=d3e534808-122878

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