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Employee Benefit Plans (Textual) (Details) $ in Thousands | 12 Months Ended
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Dec. 31, 2019 USD ($) plan shares | Dec. 31, 2018 USD ($) shares
Defined Benefit Plan Disclosure [Line Items] |  |
Deferred compensation arrangements, overall, description | After one year of service the Company matches 100% of employee contributions up to 3% of compensation and 50% of employee contributions on the next 2% of compensation. |
Number of stock option plans | plan | 1 |
Options vested in period, fair value | $ 317 | $ 244
Deferred tax expense from stock options exercised | 61 | 319
Options, exercises in period, intrinsic value | 372 | $ 1,500
Options, outstanding, intrinsic value | 1,800 |
Options, exercisable, intrinsic value | 1,800 |
Proceeds from stock options exercised | $ 374 |
Number of shares granted (in shares) | shares | 0 | 0
Vested (in shares) | shares |  | 0
Director [Member] |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Direct stock grant expense | $ 65 | $ 9
Deferred Salary Reduction Plan [Member] |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Defined contribution plan, cost recognized | 818 | 716
Stock Options [Member] |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Share-based compensation expense | 121 | 134
Stock Appreciation Rights (SARs) [Member] |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Share-based compensation expense | 134 | 34
Restricted Stock [Member] |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Share-based compensation expense | 396 | $ 263
Unrecognized compensation cost | $ 844 |
Unrecognized compensation costs, period for recognition | 3 years 2 months 4 days |
Grant-date fair value | $ 63 |
Vested (in shares) | shares | 3,000 |
2015 Stock Incentive Plan [Member] |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Rights issued (in shares) | shares | 33,059 |
Rights available for grant (in shares) | shares | 1,916,507 |
Cornerstone Bancshares, Inc. Long-Term Incentive Plan [Member] |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Rights issued (in shares) | shares | 38,250 |
Cornerstone Non-Qualified Plan Options [Member] |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Rights issued (in shares) | shares | 51,750 |
Capstone Stock Option Plan [Member] |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Rights issued (in shares) | shares | 13,599 |
401 (k) Matching Range One [Member] | Deferred Salary Reduction Plan [Member] |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Request service period | 1 year |
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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- Definition General description of deferred compensation arrangements. Deferred compensation represents currently earned compensation that, under the terms of a profit-sharing, rabbi trust, pension, employee contract, or equity-based (including stock or unit option) plan, is not actually paid until a later date and is therefore not taxable until that date. May also include some split-dollar life insurance arrangements. This type of arrangement is usually made to help employees postpone paying taxes on the income and also to retain employees longer. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=116856206&loc=d3e5047-113901 + Details
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- Definition The difference between the maximum number of shares (or other type of equity) authorized for issuance under the plan (including the effects of amendments and adjustments), and the sum of: 1) the number of shares (or other type of equity) already issued upon exercise of options or other equity-based awards under the plan; and 2) shares (or other type of equity) reserved for issuance on granting of outstanding awards, net of cancellations and forfeitures, if applicable. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=116856206&loc=d3e5070-113901 + Details
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