Document and Entity Information - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Jun. 30, 2019	Mar. 04, 2019
Details
Registrant Name	GREAT SOUTHERN BANCORP, INC.
Registrant CIK	0000854560
SEC Form	10-K
Period End date	Dec. 31, 2019
Fiscal Year End	--12-31
Trading Symbol	gsbc
Tax Identification Number (TIN)	43-1524856
Number of common stock shares outstanding			14,212,780
Public Float		$ 658,342,279
Filer Category	Accelerated Filer
Current with reporting	Yes
Voluntary filer	No
Well-known Seasoned Issuer	No
Shell Company	false
Small Business	false
Emerging Growth Company	false
Entity File Number	0-18082
Entity Incorporation, State or Country Code	MD
Entity Address, Address Line One	1451 E. 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
Phone Fax Number Description	Registrant's telephone number
Title of 12(b) Security	Common Stock
Security Exchange Name	NASDAQ
Entity Interactive Data Current	Yes
Amendment Flag	false
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	FY
Document Annual Report	true
Document Transition Report	false