| Document and Entity Information | Jun. 17, 2020 |
| Details | |
| Registrant CIK | 0000854560 |
| Registrant Name | GREAT SOUTHERN BANCORP, INC. |
| SEC Form | 8-K |
| Period End date | Jun. 17, 2020 |
| Trading Symbol | GSBC |
| Trading Exchange | NASDAQ |
| Tax Identification Number (TIN) | 43-1524856 |
| Emerging Growth Company | false |
| Entity Incorporation, State or Country Code | MD |
| Entity File Number | 0-18082 |
| Entity Address, Address Line One | 1451 East Battlefield |
| Entity Address, City or Town | Springfield |
| Entity Address, State or Province | MO |
| Entity Address, Postal Zip Code | 65804 |
| City Area Code | 417 |
| Local Phone Number | 887-4400 |
| Written Communications | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Title of 12(b) Security | Common Stock |
| Amendment Flag | false |
| Document Fiscal Year Focus | 2020 |
| Document Fiscal Period Focus | FY |
