Employee Benefit Plans (Narrative) (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2020 USD ($) plan shares	Dec. 31, 2019 USD ($) shares
Defined Benefit Plan Disclosure [Line Items]
Defined contribution plan, cost recognized	$ 1,100	$ 818
Number of stock option plans | plan	1
Share-based compensation expense	$ 121
Deferred tax benefit from stock options exercised	18	$ 61
Unrecognized compensation cost	$ 0
Shares vested (in shares) | shares	0	0
Stock Options [Member]
Defined Benefit Plan Disclosure [Line Items]
Options, exercises in period, intrinsic value	$ 190	$ 372
Options, outstanding, intrinsic value	792
Options, exercisable, intrinsic value	792
Proceeds from options exercised	339
Stock Appreciation Rights (SARs) [Member]
Defined Benefit Plan Disclosure [Line Items]
Share-based compensation expense	$ 51	$ 134
Granted (in shares) | shares	18,000	21,000
Restricted Stock [Member]
Defined Benefit Plan Disclosure [Line Items]
Share-based compensation expense	$ 482	$ 396
Unrecognized compensation cost	$ 1,000
Unrecognized compensation costs, period for recognition	2 years 10 months 6 days
Grant-date fair value	$ 134
Vested (in shares) | shares	7,295
2015 Stock Incentive Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Rights issued (in shares) | shares	26,601
Rights available for grant (in shares) | shares	1,876,894
Cornerstone Bancshares, Inc. Long-Term Incentive Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Rights issued (in shares) | shares	30,500
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%