Regulatory Matters (Regulatory capital amounts and ratios) (Details) - USD ($)	Jun. 30, 2018	Dec. 31, 2017
Tier 1 Risk-Based Core Capital (To Risk Weighted Assets)
Actual, Amount	$ 81,819,000	$ 78,790,000
Actual, Ratio	15.20%	15.7591%
For Capital Adequacy, Amount	$ 32,380,860	$ 29,997,900
For Capital Adequacy, Ratio	6.00%	6.00%
Total Risk-Based Capital (To Risk Weighted Assets)
Actual, Amount	$ 88,586,000	$ 85,066,000
Actual, Ratio	16.40%	17.01439%
For Capital Adequacy, Amount	$ 43,174,480	$ 39,997,200
For Capital Adequacy, Ratio	8.00%	8.00%
Common Equity Tier One Capital	$ 76,819,000	$ 73,790,000
Common Equity Tier One Capital Ratio	14.20%	14.75903%
Common Equity Tier One Capital Required for Capital Adequacy	$ 24,285,645	$ 22,498,425
Tier 1 Leverage (Core) Capital (To Adjusted Tangible Assets)
Actual, Amount	$ 81,819,000	$ 78,790,000
Actual, Ratio	9.30%	9.13019%
For Capital Adequacy, Amount	$ 35,324,800	$ 34,518,440
For Capital Adequacy, Ratio	4.00%	4.00%
Security Federal Bank [Member]
Tier 1 Risk-Based Core Capital (To Risk Weighted Assets)
Actual, Amount	$ 88,390,000	$ 88,275,000
Actual, Ratio	16.38293%	17.66175%
For Capital Adequacy, Amount	$ 32,371,500	$ 29,988,540
For Capital Adequacy, Ratio	6.00%	6.00%
To Be Well Capitalized Under Prompt Corrective Action Provisions, Amount	$ 43,162,000	$ 39,985,000
To Be Well Capitalized Under Prompt Corrective Action Provisions, Ratio	8.00%	8.00%
Total Risk-Based Capital (To Risk Weighted Assets)
Actual, Amount	$ 95,157,000	$ 94,547,000
Actual, Ratio	17.63718%	18.91663%
For Capital Adequacy, Amount	$ 43,162,000	$ 39,984,720
For Capital Adequacy, Ratio	8.00%	8.00%
To Be Well Capitalized Under Prompt Corrective Action Provisions, Amount	$ 53,953,000	$ 49,981,000
To Be Well Capitalized Under Prompt Corrective Action Provisions, Ratio	10.00%	10.00%
Common Equity Tier One Capital	$ 88,390,000	$ 88,275,000
Common Equity Tier One Capital Ratio	16.38293%	17.66175%
Common Equity Tier One Capital Required for Capital Adequacy	$ 24,278,625	$ 22,491,405
Common Equity Tier One Capital Required to be Well-Capitalized	35,069,000	32,488,000
Tier 1 Leverage (Core) Capital (To Adjusted Tangible Assets)
Actual, Amount	$ 88,390,000	$ 88,275,000
Actual, Ratio	10.0106%	10.23116%
For Capital Adequacy, Amount	$ 35,318,560	$ 34,512,200
For Capital Adequacy, Ratio	4.00%	4.00%
To Be Well Capitalized Under Prompt Corrective Action Provisions, Amount	$ 44,148,000	$ 43,140,000
To Be Well Capitalized Under Prompt Corrective Action Provisions, Ratio	5.00%	5.00%