Regulatory Matters - Schedule of Compliance with Regulatory Capital Requirements under Banking Regulations (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Total capital Member | Great Southern Bancorp, Inc. Member
Actual Capital Amount	$ 745,641	$ 800,388
Actual Capital Ratio	16.30%	17.20%
Capital Required for Capital Adequacy	$ 365,120	$ 373,132
Capital Required for Capital Adequacy to Risk Weighted Assets	8.0	8.0
Total capital Member | Great Southern Bank Member
Actual Capital Amount	$ 701,215	$ 694,047
Actual Capital Ratio	15.40%	14.90%
Capital Required for Capital Adequacy	$ 365,048	$ 373,058
Capital Required for Capital Adequacy to Risk Weighted Assets	8.0	8.0
Capital Required to be Well Capitalized	$ 456,310	$ 466,322
Capital Required to be Well Capitalized to Risk Weighted Assets	10.0	10.0
Tier I capital Member | Great Southern Bancorp, Inc. Member
Actual Capital Amount	$ 613,544	$ 594,645
Actual Capital Ratio	13.40%	12.70%
Capital Required for Capital Adequacy	$ 273,840	$ 279,849
Capital Required for Capital Adequacy to Risk Weighted Assets	6.0	6.0
Tier I capital Member | Great Southern Bank Member
Actual Capital Amount	$ 644,134	$ 638,304
Actual Capital Ratio	14.10%	13.70%
Capital Required for Capital Adequacy	$ 273,786	$ 279,793
Capital Required for Capital Adequacy to Risk Weighted Assets	6.0	6.0
Capital Required to be Well Capitalized	$ 365,048	$ 373,058
Capital Required to be Well Capitalized to Risk Weighted Assets	8.0	8.0
Tier I leverage capital Member | Great Southern Bancorp, Inc. Member
Actual Capital Amount	$ 613,544	$ 594,645
Actual Capital Ratio	11.30%	10.90%
Capital Required for Capital Adequacy	$ 217,264	$ 217,223
Capital Required for Capital Adequacy to Risk Weighted Assets	4.0	4.0
Tier I leverage capital Member | Great Southern Bank Member
Actual Capital Amount	$ 644,134	$ 638,304
Actual Capital Ratio	11.90%	11.80%
Capital Required for Capital Adequacy	$ 217,209	$ 217,170
Capital Required for Capital Adequacy to Risk Weighted Assets	4.0	4.0
Capital Required to be Well Capitalized	$ 271,511	$ 271,463
Capital Required to be Well Capitalized to Risk Weighted Assets	5.0	5.0
Common equity Tier I capital Member | Great Southern Bancorp, Inc. Member
Actual Capital Amount	$ 588,544	$ 569,645
Actual Capital Ratio	12.90%	12.20%
Capital Required for Capital Adequacy	$ 205,380	$ 209,887
Capital Required for Capital Adequacy to Risk Weighted Assets	4.5	4.5
Common equity Tier I capital Member | Great Southern Bank Member
Actual Capital Amount	$ 644,134	$ 638,304
Actual Capital Ratio	14.10%	13.70%
Capital Required for Capital Adequacy	$ 205,340	$ 209,845
Capital Required for Capital Adequacy to Risk Weighted Assets	4.5	4.5
Capital Required to be Well Capitalized	$ 296,602	$ 303,109
Capital Required to be Well Capitalized to Risk Weighted Assets	6.5	6.5