Regulatory Matters (Regulatory capital amounts and ratios) (Details) - Security Federal Bank [Member]	Mar. 31, 2021 USD ($)	Dec. 31, 2020 USD ($)
Tier 1 Risk-Based Core Capital (To Risk Weighted Assets)
Actual, Amount	$ 113,186,000	$ 109,673,000
Actual, Ratio	0.184	0.186
For Capital Adequacy, Amount	$ 36,878,000	$ 35,330,000
For Capital Adequacy, Ratio	0.060	0.060
To Be Well Capitalized Under Prompt Corrective Action Provisions, Amount	$ 49,171,000	$ 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	$ 120,921,000	$ 117,101,000
Actual, Ratio	0.197	0.199
For Capital Adequacy, Amount	$ 49,171,000	$ 47,107,000
For Capital Adequacy, Ratio	0.080	0.080
To Be Well Capitalized Under Prompt Corrective Action Provisions, Amount	$ 61,464,000	$ 58,884,000
To Be Well Capitalized Under Prompt Corrective Action Provisions, Ratio	0.100	0.100
Common Equity Tier One Capital	$ 113,186,000	$ 109,673,000
Common Equity Tier One Capital Ratio	0.184	0.186
Common Equity Tier One Capital Required for Capital Adequacy	$ 27,659,000	$ 26,498,000
Common Equity Tier One Capital Required to be Well-Capitalized	39,952,000	38,275,000
Tier 1 Leverage (Core) Capital (To Adjusted Tangible Assets)
Actual, Amount	$ 113,186,000	$ 109,673,000
Actual, Ratio	0.098	0.098
For Capital Adequacy, Amount	$ 46,218,000	$ 44,957,000
For Capital Adequacy, Ratio	0.040	0.040
To Be Well Capitalized Under Prompt Corrective Action Provisions, Amount	$ 57,773,000	$ 56,197,000
To Be Well Capitalized Under Prompt Corrective Action Provisions, Ratio	0.050	0.050