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%