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Employee Benefit Plans (Narrative) (Details) $ in Thousands | 3 Months Ended | 9 Months Ended
--- | --- | ---
Sep. 30, 2021 USD ($) shares | Sep. 30, 2020 USD ($) | Sep. 30, 2021 USD ($) plan shares | Sep. 30, 2020 USD ($) shares
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Contribution to the Plan | $ 287 | $ 282 | $ 925 | $ 840
Number of stock option plans | plan |  |  | 1 |
Deferred tax expense from stock options exercised |  | 3 |  |
Deferred tax benefit from stock options exercised |  |  | $ 9 | $ 19
Unrecognized compensation cost | 0 |  | $ 0 |
Shares vested (in shares) | shares |  |  | 0 | 0
Stock Options [Member] |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Share-based compensation expense | 0 | 0 | $ 0 | $ 0
Options, exercises in period, intrinsic value |  | 75 | 220 | 141
Options, outstanding, intrinsic value | $ 1,300 |  | 1,300 |
Proceeds from options exercised |  |  | 194 |
Exercise of options | shares | 0 |  |  |
Stock Appreciation Rights (SARs) [Member] |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Share-based compensation expense | $ 49 | (63) | $ 162 |
Share-based compensation income |  |  |  | (89)
Granted (in shares) | shares |  |  | 22,000 |
Exercise of options | shares |  |  | 23,500 |
Restricted Stock [Member] |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Share-based compensation expense | 163 | $ 142 | $ 525 | $ 365
Unrecognized compensation cost | $ 1,600 |  | $ 1,600 |
Unrecognized compensation costs, period for recognition |  |  | 2 years 8 months 26 days |
Grant-date fair value |  |  | $ 154 |
Vested (in shares) | shares |  |  | 7,185 |
2015 Stock Incentive Plan [Member] |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Rights available for grant (in shares) | shares | 1,830,260 |  | 1,830,260 |
Cornerstone Bancshares, Inc. Long-Term Incentive Plan [Member] |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Rights issued (in shares) | shares |  |  | 19,250 |
Cornerstone Non-Qualified Plan Options [Member] |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Rights issued (in shares) | shares |  |  | 40,250 |
Capstone Stock Option Plan [Member] |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Rights issued (in shares) | shares |  |  | 2,266 |
401 (k) Matching Range One [Member] | Deferred Salary Reduction Plan [Member] |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Employer matching contribution, percent of match |  |  | 100.00% |
Employer matching contribution, percent of employees gross pay |  |  | 3.00% |
401 (k) Matching Range Two [Member] | Deferred Salary Reduction Plan [Member] |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Employer matching contribution, percent of match |  |  | 50.00% |
Employer matching contribution, percent of employees gross pay |  |  | 2.00% |

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