Concentrations of Credit Risk (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2020	Dec. 31, 2019
Concentration Risk [Line Items]
Credit extending terms to borrowers	The Bank, as a matter of policy, does not generally extend credit to any single borrower or group of related borrowers in excess of 25% of statutory capital, or approximately
Percentage of statutory capital	25.00%
Credit extending terms, maximum amount of statutory capital	$ 95.6
Commercial Real Estate [Member]
Concentration Risk [Line Items]
Concentration risk (as a percent)	51.00%	56.00%
Loan Portfolio Secured by Real Estate [Member]
Concentration Risk [Line Items]
Concentration risk (as a percent)	72.00%

The element represents the terms and conditions for extending credit borrowers.

No definition available.

Name:	smbk_CreditExtendingTermsToBorrowers
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Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Statutory Capital, Maximum Limit To Extend Credit To Borrowers, Amount

+ References

No definition available.

+ Details

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Namespace Prefix:	smbk_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Statutory Capital, Maximum Limit To Extend Credit To Borrowers, Percent

+ References

No definition available.

+ Details

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Data Type:	num:percentItemType
Balance Type:	na
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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

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- Definition

For an entity that discloses a concentration risk in relation to quantitative amount, which serves as the "benchmark" (or denominator) in the equation, this concept represents the concentration percentage derived from the division.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 275
-SubTopic 10
-Section 50
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Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
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-Name Accounting Standards Codification
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Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
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Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
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-Name Accounting Standards Codification
-Topic 275
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-URI http://asc.fasb.org/extlink&oid=99393423&loc=d3e6404-108592

+ Details

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Period Type:	duration

- Details

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Namespace Prefix:
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Balance Type:
Period Type:

- Details

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