Regulatory Matters (Regulatory Capital Levels) (Details) $ in Thousands	Sep. 30, 2021 USD ($)	Dec. 31, 2020 USD ($)
SmartFinancial, Inc. [Member]
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Total Capital (to Risk-Weighted Assets), Actual Amount	$ 381,766	$ 329,431
Tier 1 Capital (to Risk-Weighted Assets), Actual Amount	320,562	271,739
Common Equity Tier 1 Capital (to Risk-Weighted Assets), Actual Amount	320,562	271,739
Tier 1 Capital (to Average Assets), Actual Amount	$ 320,562	$ 271,739
Total Capital (to Risk-Weighted Assets), Actual Ratio (as a percent)	12.92	14.07
Tier 1 Capital (to Risk-Weighted Assets), Actual Ratio (as a percent)	10.85	11.61
Common Equity Tier 1 Capital (to Risk-Weighted Assets), Actual Ratio (as a percent)	10.85%	11.61%
Tier 1 Capital (to Average Assets), Actual Ratio (as a percent)	8.36	8.70
Total Capital (to Risk-Weighted Assets), Minimum for capital adequacy purposes Amount	$ 236,367	$ 187,303
Tier 1 Capital (to Risk-Weighted Assets), Minimum for capital adequacy purposes Amount	177,275	140,477
Common Equity Tier 1 Capital (to Risk-Weighted Assets), Minimum for capital adequacy purposes Amount	132,956	105,358
Tier 1 Capital (to Average Assets), Minimum for capital adequacy purposes Amount	$ 153,417	$ 125,002
Total Capital (to Risk-Weighted Assets), Minimum for capital adequacy purposes Ratio (as a percent)	8.00	8.00
Tier 1 Capital (to Risk-Weighted Assets), Minimum for capital adequacy purposes Ratio (as a percent)	6.00	6.00
Common Equity Tier 1 Capital (to Risk-Weighted Assets), Minimum for capital adequacy purposes Ratio (as a percent)	4.50%	4.50%
Tier 1 Capital (to Average Assets), Minimum for capital adequacy purposes Ratio (as a percent)	4.00	4.00
Smart Bank [Member]
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Total Capital (to Risk-Weighted Assets), Actual Amount	$ 371,740	$ 317,660
Tier 1 Capital (to Risk-Weighted Assets), Actual Amount	352,445	299,314
Common Equity Tier 1 Capital (to Risk-Weighted Assets), Actual Amount	352,445	299,314
Tier 1 Capital (to Average Assets), Actual Amount	$ 352,445	$ 299,314
Total Capital (to Risk-Weighted Assets), Actual Ratio (as a percent)	12.59	13.57
Tier 1 Capital (to Risk-Weighted Assets), Actual Ratio (as a percent)	11.94	12.78
Common Equity Tier 1 Capital (to Risk-Weighted Assets), Actual Ratio (as a percent)	11.94%	12.78%
Tier 1 Capital (to Average Assets), Actual Ratio (as a percent)	9.20	9.58
Total Capital (to Risk-Weighted Assets), Minimum for capital adequacy purposes Amount	$ 236,244	$ 187,294
Tier 1 Capital (to Risk-Weighted Assets), Minimum for capital adequacy purposes Amount	177,183	140,470
Common Equity Tier 1 Capital (to Risk-Weighted Assets), Minimum for capital adequacy purposes Amount	132,887	105,353
Tier 1 Capital (to Average Assets), Minimum for capital adequacy purposes Amount	$ 153,185	$ 124,969
Total Capital (to Risk-Weighted Assets), Minimum for capital adequacy purposes Ratio (as a percent)	8.00	8.00
Tier 1 Capital (to Risk-Weighted Assets), Minimum for capital adequacy purposes Ratio (as a percent)	6.00	6.00
Common Equity Tier 1 Capital (to Risk-Weighted Assets), Minimum for capital adequacy purposes Ratio (as a percent)	4.50%	4.50%
Tier 1 Capital (to Average Assets), Minimum for capital adequacy purposes Ratio (as a percent)	4.00	4.00
Total Capital (to Risk-Weighted Assets), Minimum to be well capitalized under prompt corrective action provisions Amount	$ 295,304	$ 234,117
Tier 1 Capital (to Risk-Weighted Assets), Minimum to be well capitalized under prompt corrective action provisions Amount	236,244	187,294
Common Equity Tier 1 Capital (to Risk-Weighted Assets), Minimum to be well capitalized under prompt corrective action provisions Amount	191,948	152,176
Tier 1 Capital (to Average Assets), Minimum to be well capitalized under prompt corrective action provisions Amount	$ 191,481	$ 156,212
Total Capital (to Risk-Weighted Assets), Minimum to be well capitalized under prompt corrective action provisions Ratio (as a percent)	10.00	10.00
Tier 1 Capital (to Risk-Weighted Assets), Minimum to be well capitalized under prompt corrective action provisions Ratio (as a percent)	8.00	8.00
Common Equity Tier 1 Capital (to Risk-Weighted Assets), Minimum to be well capitalized under prompt corrective action provisions Ratio (as a percent)	6.50%	6.50%
Tier 1 Capital (to Average Assets), Minimum to be well capitalized under prompt corrective action provisions Ratio (as a percent)	5.00	5.00

Common equity Tier 1 Risk Based Capital as defined in the regulations.

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The minimum amount of common equity Tier 1 Risk Based Capital required for capital adequacy purposes under the regulatory framework for prompt corrective action.

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The minimum common equity Tier One Capital Ratio (Common equity Tier one capital divided by risk-weighted assets) required for capital adequacy purposes under the regulatory framework for prompt corrective action.

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The amount of common equity Tier 1 Risk Based Capital required to be categorized as well capitalized under the regulatory framework for prompt corrective action.

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The Common equity Tier 1 capital ratio (common equity Tier 1 capital divided by risk weighted assets) required to be categorized as "well capitalized" under the regulatory framework for prompt corrective action.

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Common equity Tier 1 capital divided by risk weighted assets as defined by regulations.

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Amount of total capital as defined by regulatory framework.

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Amount of minimum total risk-based capital required for capital adequacy as defined by regulatory framework.

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Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 505
-Section 50
-Paragraph 1
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Ratio of minimum total risk-based capital to risk-weighted assets required for capital adequacy as defined by regulatory framework.

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Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
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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.

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Amount of Tier 1 leverage capital as defined by regulatory framework.

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