Regulatory Matters (Regulatory capital amounts and ratios) (Details) - Security Federal Bank [Member] - USD ($)	Sep. 30, 2020	Dec. 31, 2019
Tier 1 Risk-Based Core Capital (To Risk Weighted Assets)
Actual, Amount	$ 106,276,000	$ 101,280,000
Actual, Ratio	18.30%	18.20%
For Capital Adequacy, Amount	$ 34,800,000	$ 33,418,000
For Capital Adequacy, Ratio	6.00%	6.00%
To Be Well Capitalized Under Prompt Corrective Action Provisions, Amount	$ 46,401,000	$ 44,558,000
To Be Well Capitalized Under Prompt Corrective Action Provisions, Ratio	8.00%	8.00%
Total Risk-Based Capital (To Risk Weighted Assets)
Actual, Amount	$ 113,595,000	$ 108,270,000
Actual, Ratio	19.60%	19.40%
For Capital Adequacy, Amount	$ 46,401,000	$ 44,558,000
For Capital Adequacy, Ratio	8.00%	8.00%
To Be Well Capitalized Under Prompt Corrective Action Provisions, Amount	$ 58,001,000	$ 55,697,000
To Be Well Capitalized Under Prompt Corrective Action Provisions, Ratio	10.00%	10.00%
Common Equity Tier One Capital	$ 106,276,000	$ 101,280,000
Common Equity Tier One Capital Ratio	18.30%	18.20%
Common Equity Tier One Capital Required for Capital Adequacy	$ 26,100,000	$ 25,064,000
Common Equity Tier One Capital Required to be Well-Capitalized	37,701,000	36,203,000
Tier 1 Leverage (Core) Capital (To Adjusted Tangible Assets)
Actual, Amount	$ 106,276,000	$ 101,280,000
Actual, Ratio	9.70%	10.40%
For Capital Adequacy, Amount	$ 43,787,000	$ 39,134,000
For Capital Adequacy, Ratio	4.00%	4.00%
To Be Well Capitalized Under Prompt Corrective Action Provisions, Amount	$ 54,734,000	$ 48,917,000
To Be Well Capitalized Under Prompt Corrective Action Provisions, Ratio	5.00%	5.00%