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%