Document and Entity Information - $ / shares		9 Months Ended
	Nov. 04, 2020	Sep. 30, 2020
Details
Registrant CIK		0000854560
Fiscal Year End		--12-31
Registrant Name		GREAT SOUTHERN BANCORP, INC.
SEC Form		10-Q
Period End date		Sep. 30, 2020
Trading Symbol		GSBC
Trading Exchange		NASDAQ
Tax Identification Number (TIN)		43-1524856
Number of common stock shares outstanding	13,844,270
Filer Category		Accelerated Filer
Current with reporting		Yes
Interactive Data Current		Yes
Shell Company		false
Small Business		false
Emerging Growth Company		false
Document Quarterly Report		true
Document Transition Report		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
Title of 12(b) Security		Common Stock
Entity Listing, Par Value Per Share	$ 0.01
Amendment Flag		false
Document Fiscal Year Focus		2020
Document Fiscal Period Focus		Q3