Regulatory Matters (Regulatory capital amounts and ratios) (Details) - Security Federal Bank [Member] - USD ($)	Mar. 31, 2019	Dec. 31, 2018
Tier 1 Risk-Based Core Capital (To Risk Weighted Assets)
Actual, Amount	$ 89,832,000	$ 89,188,000
Actual, Ratio	16.12516%	16.21346%
For Capital Adequacy, Amount	$ 33,425,520	$ 33,005,160
For Capital Adequacy, Ratio	6.00%	6.00%
To Be Well Capitalized Under Prompt Corrective Action Provisions, Amount	$ 44,567,000	$ 44,007,000
To Be Well Capitalized Under Prompt Corrective Action Provisions, Ratio	8.00%	8.00%
Total Risk-Based Capital (To Risk Weighted Assets)
Actual, Amount	$ 96,818,000	$ 96,092,000
Actual, Ratio	17.37918%	17.46854%
For Capital Adequacy, Amount	$ 44,567,360	$ 44,006,880
For Capital Adequacy, Ratio	8.00%	8.00%
To Be Well Capitalized Under Prompt Corrective Action Provisions, Amount	$ 55,709,000	$ 55,009,000
To Be Well Capitalized Under Prompt Corrective Action Provisions, Ratio	10.00%	10.00%
Common Equity Tier One Capital	$ 89,832,000	$ 89,188,000
Common Equity Tier One Capital Ratio	16.12516%	16.21346%
Common Equity Tier One Capital Required for Capital Adequacy	$ 25,069,140	$ 24,753,870
Common Equity Tier One Capital Required to be Well-Capitalized	36,211,000	35,756,000
Tier 1 Leverage (Core) Capital (To Adjusted Tangible Assets)
Actual, Amount	$ 89,832,000	$ 89,188,000
Actual, Ratio	9.77609%	9.77765%
For Capital Adequacy, Amount	$ 36,755,800	$ 36,486,480
For Capital Adequacy, Ratio	4.00%	4.00%
To Be Well Capitalized Under Prompt Corrective Action Provisions, Amount	$ 45,945,000	$ 45,608,000
To Be Well Capitalized Under Prompt Corrective Action Provisions, Ratio	5.00%	5.00%