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Employee Benefit Plans (Narrative) (Details) $ in Thousands | 3 Months Ended | 6 Months Ended
--- | --- | ---
Jun. 30, 2021 USD ($) shares | Jun. 30, 2020 USD ($) | Jun. 30, 2021 USD ($) plan shares | Jun. 30, 2020 USD ($) shares
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Contribution to the Plan | $ 350 | $ 307 | $ 638 | $ 558
Number of stock option plans | plan |  |  | 1 |
Deferred tax expense from stock options exercised |  | 2 |  |
Deferred tax benefit from stock options exercised | 8 |  | $ 9 | $ 22
Unrecognized compensation cost | 0 |  | $ 0 |
Shares vested (in shares) | shares |  |  | 0 | 0
Stock Options [Member] |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Options, exercises in period, intrinsic value | 27 | 2 | $ 220 | $ 66
Options, outstanding, intrinsic value | 1,100 |  | 1,100 |
Proceeds from options exercised |  |  | 194 |
Stock Appreciation Rights (SARs) [Member] |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Share-based compensation expense | 64 | 92 | $ 113 |
Share-based compensation income |  |  |  | (26)
Granted (in shares) | shares |  |  | 22,000 |
Restricted Stock [Member] |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Share-based compensation expense | 162 | $ 113 | $ 363 | $ 223
Unrecognized compensation cost | $ 1,700 |  | $ 1,700 |
Unrecognized compensation costs, period for recognition |  |  | 2 years 11 months 26 days |
Grant-date fair value |  |  | $ 133 |
Vested (in shares) | shares |  |  | 5,985 |
2015 Stock Incentive Plan [Member] |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Rights issued (in shares) | shares |  |  | 18,811 |
Rights available for grant (in shares) | shares | 1,832,427 |  | 1,832,427 |
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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