Regulatory Matters - Schedule of Compliance with Regulatory Capital Requirements under Banking Regulations (Details) - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021
Total capital | Great Southern Bancorp, Inc.
Regulatory Matters
Actual Capital Amount	$ 746,287	$ 745,641
Actual Capital Ratio	13.50%	16.30%
Capital Required for Capital Adequacy	$ 440,767	$ 365,120
Capital Required for Capital Adequacy to Risk Weighted Assets	0.080	0.080
Total capital | Great Southern Bank
Regulatory Matters
Actual Capital Amount	$ 721,616	$ 701,215
Actual Capital Ratio	13.10%	15.40%
Capital Required for Capital Adequacy	$ 440,683	$ 365,048
Capital Required for Capital Adequacy to Risk Weighted Assets	0.080	0.080
Capital Required to be Well Capitalized	$ 550,854	$ 456,310
Capital Required to be Well Capitalized to Risk Weighted Assets	0.100	0.100
Tier I capital | Great Southern Bancorp, Inc.
Regulatory Matters
Actual Capital Amount	$ 607,807	$ 613,544
Actual Capital Ratio	11.00%	13.40%
Capital Required for Capital Adequacy	$ 330,575	$ 273,840
Capital Required for Capital Adequacy to Risk Weighted Assets	0.060	0.060
Tier I capital | Great Southern Bank
Regulatory Matters
Actual Capital Amount	$ 658,136	$ 644,134
Actual Capital Ratio	11.90%	14.10%
Capital Required for Capital Adequacy	$ 330,512	$ 273,786
Capital Required for Capital Adequacy to Risk Weighted Assets	0.060	0.060
Capital Required to be Well Capitalized	$ 440,683	$ 365,048
Capital Required to be Well Capitalized to Risk Weighted Assets	0.080	0.080
Tier I leverage capital | Great Southern Bancorp, Inc.
Regulatory Matters
Actual Capital Amount	$ 607,807	$ 613,544
Actual Capital Ratio	10.60%	11.30%
Capital Required for Capital Adequacy	$ 228,673	$ 217,264
Capital Required for Capital Adequacy to Risk Weighted Assets	0.040	0.040
Tier I leverage capital | Great Southern Bank
Regulatory Matters
Actual Capital Amount	$ 658,136	$ 644,134
Actual Capital Ratio	11.50%	11.90%
Capital Required for Capital Adequacy	$ 228,511	$ 217,209
Capital Required for Capital Adequacy to Risk Weighted Assets	0.040	0.040
Capital Required to be Well Capitalized	$ 285,638	$ 271,511
Capital Required to be Well Capitalized to Risk Weighted Assets	0.050	0.050
Common equity Tier I capital | Great Southern Bancorp, Inc.
Regulatory Matters
Actual Capital Amount	$ 582,807	$ 588,544
Actual Capital Ratio	10.60%	12.90%
Capital Required for Capital Adequacy	$ 247,932	$ 205,380
Capital Required for Capital Adequacy to Risk Weighted Assets	0.045	0.045
Common equity Tier I capital | Great Southern Bank
Regulatory Matters
Actual Capital Amount	$ 658,136	$ 644,134
Actual Capital Ratio	11.90%	14.10%
Capital Required for Capital Adequacy	$ 247,884	$ 205,340
Capital Required for Capital Adequacy to Risk Weighted Assets	0.045	0.045
Capital Required to be Well Capitalized	$ 358,055	$ 296,602
Capital Required to be Well Capitalized to Risk Weighted Assets	0.065	0.065