Stockholders' Equity and Regulatory Capital (Details) $ in Thousands	Jun. 30, 2022 USD ($)	Jun. 30, 2021 USD ($)
Southern Bank \| Total Capital (to Risk-Weighted Assets)
Capital	$ 352,169	$ 308,482
Capital to Risk Weighted Assets	0.1290	0.1396
Capital Required for Capital Adequacy	$ 218,397	$ 176,816
Capital Required for Capital Adequacy to Risk Weighted Assets	0.0800	0.0800
Capital Required to be Well Capitalized	$ 272,996	$ 221,019
Capital Required to be Well Capitalized to Risk Weighted Assets	0.1000	0.1000
Southern Bank \| Tier I Capital (to Risk-Weighted Assets)
Capital	$ 325,183	$ 282,638
Capital to Risk Weighted Assets	0.1191	0.1279
Capital Required for Capital Adequacy	$ 163,797	$ 132,612
Capital Required for Capital Adequacy to Risk Weighted Assets	0.0600	0.0600
Capital Required to be Well Capitalized	$ 218,397	$ 176,816
Capital Required to be Well Capitalized to Risk Weighted Assets	0.0800	0.0800
Southern Bank \| Tier I Capital (to Average Assets)
Capital	$ 325,183	$ 282,638
Capital to Risk Weighted Assets	0.1022	0.1043
Capital Required for Capital Adequacy	$ 127,333	$ 108,369
Capital Required for Capital Adequacy to Risk Weighted Assets	0.0400	0.0400
Capital Required to be Well Capitalized	$ 159,167	$ 135,461
Capital Required to be Well Capitalized to Risk Weighted Assets	0.0500	0.0500
Southern Bank \| Common Equity Tier I Capital (to Risk-Weighted Assets)
Capital	$ 325,183	$ 282,638
Capital to Risk Weighted Assets	0.1191	0.1279
Capital Required for Capital Adequacy	$ 122,848	$ 99,459
Capital Required for Capital Adequacy to Risk Weighted Assets	0.0450	0.0450
Capital Required to be Well Capitalized	$ 177,447	$ 143,663
Capital Required to be Well Capitalized to Risk Weighted Assets	0.0650	0.00650
Consolidated \| Total Capital (to Risk-Weighted Assets)
Capital	$ 370,013	$ 315,490
Capital to Risk Weighted Assets	0.1342	0.1418
Capital Required for Capital Adequacy	$ 220,558	$ 177,938
Capital Required for Capital Adequacy to Risk Weighted Assets	0.0800	0.0800
Consolidated \| Tier I Capital (to Risk-Weighted Assets)
Capital	$ 335,316	$ 287,701
Capital to Risk Weighted Assets	0.1216	0.1293
Capital Required for Capital Adequacy	$ 165,418	$ 133,453
Capital Required for Capital Adequacy to Risk Weighted Assets	0.0600	0.0600
Consolidated \| Tier I Capital (to Average Assets)
Capital	$ 335,316	$ 287,701
Capital to Risk Weighted Assets	0.1041	0.1061
Capital Required for Capital Adequacy	$ 128,822	$ 108,505
Capital Required for Capital Adequacy to Risk Weighted Assets	0.0400	0.0400
Consolidated \| Common Equity Tier I Capital (to Risk-Weighted Assets)
Capital	$ 319,971	$ 272,458
Capital to Risk Weighted Assets	0.1161	0.1225
Capital Required for Capital Adequacy	$ 124,064	$ 100,090
Capital Required for Capital Adequacy to Risk Weighted Assets	0.0450	0.0450

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