Regulatory Matters (Regulatory Capital Levels) (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
SmartFinancial, Inc. [Member]
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Total Capital (to Risk-Weighted Assets), Actual Amount	$ 306,982	$ 287,937
Tier 1 Capital (to Risk-Weighted Assets), Actual Amount	254,268	238,433
Common Equity Tier 1 Capital (to Risk-Weighted Assets, Actual Amount	254,268	238,433
Tier 1 Capital (to Average Assets, Actual Amount	$ 254,268	$ 238,433
Total Capital (to Risk-Weighted Assets), Actual Ratio (as a percent)	13.13%	14.02%
Tier 1 Capital (to Risk-Weighted Assets, Actual Ratio (as a percent)	10.87%	11.61%
Common Equity Tier 1 Capital (to Risk-Weighted Assets), Actual Ratio (as a percent)	10.87%	11.61%
Tier 1 Capital (to Average Assets), Actual Ratio (as a percent)	10.28%	10.34%
Total Capital (to risk-Weighted Assets), Minimum capital adequacy purposes amount	$ 187,099	$ 164,313
Tier 1 Capital (to Risk-Weighted Assets), Minimum for capital adequacy purposes, amount	140,324	123,235
Common Equity Tier 1 Capital (to Risk-Weighted Assets), Minimum for capital adequacy purposes, amount	105,243	92,426
Tier 1 Capital (to Average Assets), Minimum for capital adequacy purposes, amount	$ 98,934	$ 92,258
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	$ 295,105	$ 273,432
Tier 1 Capital (to Risk-Weighted Assets), Actual Amount	281,674	263,189
Common Equity Tier 1 Capital (to Risk-Weighted Assets, Actual Amount	281,674	263,189
Tier 1 Capital (to Average Assets, Actual Amount	$ 281,674	$ 263,189
Total Capital (to Risk-Weighted Assets), Actual Ratio (as a percent)	12.62%	13.31%
Tier 1 Capital (to Risk-Weighted Assets, Actual Ratio (as a percent)	12.05%	12.81%
Common Equity Tier 1 Capital (to Risk-Weighted Assets), Actual Ratio (as a percent)	12.05%	12.81%
Tier 1 Capital (to Average Assets), Actual Ratio (as a percent)	11.42%	11.41%
Total Capital (to risk-Weighted Assets), Minimum capital adequacy purposes amount	$ 187,077	$ 164,305
Tier 1 Capital (to Risk-Weighted Assets), Minimum for capital adequacy purposes, amount	140,308	123,229
Common Equity Tier 1 Capital (to Risk-Weighted Assets), Minimum for capital adequacy purposes, amount	105,231	92,422
Tier 1 Capital (to Average Assets), Minimum for capital adequacy purposes, amount	$ 98,636	$ 92,254
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	$ 233,847	$ 205,382
Tier 1 Capital (to Risk-Weighted Assets), Minimum to be well capitalized under prompt corrective action provisions, amount	187,077	164,305
Common Equity Tier 1 Capital (to Risk-Weighted Assets), Minimum to be well capitalized under prompt corrective action provisions, amount	152,000	133,498
Tier 1 Capital (to Average Assets), Minimum to be well capitalized under prompt corrective action provisions, amount	$ 123,295	$ 115,317
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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The amount of total capital as defined in the regulations.

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The minimum amount of Total Capital required for capital adequacy purposes under the regulatory framework for prompt corrective action.

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The minimum Total risk based capital ratio (total 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 Total Capital required to be categorized as well as capitalized under the regulatory framework for prompt corrective action.

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The Total risk based capital ratio (total capital divided by risk weighted assets) required to be categorized as "well capitalized", in the regulatory framework for prompt corrective action.

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Total Capital divided by risk weighted assets as defined in the regulations.

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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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Tier 1 Leverage Capital as defined in the regulations. Also called Core Capital.

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

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Tier 1 Leverage Capital divided by average assets as defined in the regulations.

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Tier 1 Risk Based Capital as defined in the regulations.

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

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

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