Regulatory Matters (Regulatory capital amounts and ratios) (Details) - Security Federal Bank [Member]	Sep. 30, 2021 USD ($)	Dec. 31, 2020 USD ($)
Tier 1 Risk-Based Core Capital (To Risk Weighted Assets)
Actual, Amount	$ 121,421,000	$ 109,673,000
Actual, Ratio	0.188	0.186
For Capital Adequacy, Amount	$ 38,751,000	$ 35,330,000
For Capital Adequacy, Ratio	0.060	0.060
To Be Well Capitalized Under Prompt Corrective Action Provisions, Amount	$ 51,669,000	$ 47,107,000
To Be Well Capitalized Under Prompt Corrective Action Provisions, Ratio	0.080	0.080
Total Risk-Based Capital (To Risk Weighted Assets)
Actual, Amount	$ 129,532,000	$ 117,101,000
Actual, Ratio	0.201	0.199
For Capital Adequacy, Amount	$ 51,669,000	$ 47,107,000
For Capital Adequacy, Ratio	0.080	0.080
To Be Well Capitalized Under Prompt Corrective Action Provisions, Amount	$ 64,586,000	$ 58,884,000
To Be Well Capitalized Under Prompt Corrective Action Provisions, Ratio	0.100	0.100
Common Equity Tier One Capital	$ 121,421,000	$ 109,673,000
Common Equity Tier One Capital Ratio	0.188	0.186
Common Equity Tier One Capital Required for Capital Adequacy	$ 29,064,000	$ 26,498,000
Common Equity Tier One Capital Required to be Well-Capitalized	41,981,000	38,275,000
Tier 1 Leverage (Core) Capital (To Adjusted Tangible Assets)
Actual, Amount	$ 121,421,000	$ 109,673,000
Actual, Ratio	0.102	0.098
For Capital Adequacy, Amount	$ 47,625,000	$ 44,957,000
For Capital Adequacy, Ratio	0.040	0.040
To Be Well Capitalized Under Prompt Corrective Action Provisions, Amount	$ 59,531,000	$ 56,197,000
To Be Well Capitalized Under Prompt Corrective Action Provisions, Ratio	0.050	0.050