Stockholders' Equity and Regulatory Capital (Details) $ in Thousands	Jun. 30, 2025 USD ($)	Jun. 30, 2024 USD ($)
Southern Bank \| Total Capital (to Risk-Weighted Assets)
Capital	$ 545,293	$ 496,105
Capital to Risk Weighted Assets	0.1334	0.1268
Capital Required for Capital Adequacy	$ 326,920	$ 312,877
Capital Required for Capital Adequacy to Risk Weighted Assets	0.08	0.08
Capital Required to be Well Capitalized	$ 408,650	$ 391,097
Capital Required to be Well Capitalized to Risk Weighted Assets	0.10	0.10
Southern Bank \| Tier I Capital (to Risk-Weighted Assets)
Capital	$ 494,186	$ 447,192
Capital to Risk Weighted Assets	0.1209	0.1143
Capital Required for Capital Adequacy	$ 245,190	$ 234,658
Capital Required for Capital Adequacy to Risk Weighted Assets	0.06	0.06
Capital Required to be Well Capitalized	$ 326,920	$ 312,877
Capital Required to be Well Capitalized to Risk Weighted Assets	0.08	0.08
Southern Bank \| Tier I Capital (to Average Assets)
Capital	$ 494,186	$ 447,192
Capital to Risk Weighted Assets	0.1005	0.0979
Capital Required for Capital Adequacy	$ 196,782	$ 182,723
Capital Required for Capital Adequacy to Risk Weighted Assets	0.04	0.04
Capital Required to be Well Capitalized	$ 245,977	$ 228,403
Capital Required to be Well Capitalized to Risk Weighted Assets	0.05	0.05
Southern Bank \| Common Equity Tier I Capital (to Risk-Weighted Assets)
Capital	$ 494,186	$ 447,192
Capital to Risk Weighted Assets	0.1209	0.1143
Capital Required for Capital Adequacy	$ 183,892	$ 175,993
Capital Required for Capital Adequacy to Risk Weighted Assets	0.045	0.045
Capital Required to be Well Capitalized	$ 265,622	$ 254,213
Capital Required to be Well Capitalized to Risk Weighted Assets	0.065	0.065
Consolidated \| Total Capital (to Risk-Weighted Assets)
Capital	$ 577,150	$ 524,023
Capital to Risk Weighted Assets	0.1395	0.1323
Capital Required for Capital Adequacy	$ 331,050	$ 316,979
Capital Required for Capital Adequacy to Risk Weighted Assets	0.08	0.08
Consolidated \| Tier I Capital (to Risk-Weighted Assets)
Capital	$ 517,842	$ 467,027
Capital to Risk Weighted Assets	0.1251	0.1179
Capital Required for Capital Adequacy	$ 248,288	$ 237,734
Capital Required for Capital Adequacy to Risk Weighted Assets	0.06	0.06
Consolidated \| Tier I Capital (to Average Assets)
Capital	$ 517,842	$ 467,027
Capital to Risk Weighted Assets	0.1061	0.1019
Capital Required for Capital Adequacy	$ 195,249	$ 183,262
Capital Required for Capital Adequacy to Risk Weighted Assets	0.04	0.04
Consolidated \| Common Equity Tier I Capital (to Risk-Weighted Assets)
Capital	$ 502,197	$ 451,474
Capital to Risk Weighted Assets	0.1214	0.1139
Capital Required for Capital Adequacy	$ 186,216	$ 178,300
Capital Required for Capital Adequacy to Risk Weighted Assets	0.045	0.045

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Amount of minimum total risk-based capital required for capital adequacy as defined by regulatory framework.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 942
-SubTopic 505
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (c)(1)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147477270/942-505-50-1

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
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-SubTopic 505
-Name Accounting Standards Codification
-Section 50
-Paragraph 1B
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147477270/942-505-50-1B

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