Note 27: Condensed Parent Company Statements: Condensed Cash Flow Statement -- Great Southern Bancorp, Inc. (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Gain on Redemption of Trust Preferred Securities	$ 0	$ 0	$ (1,115)
Amortization of interest rate derivative	441	289	204
Prepaid expenses and other assets	(5,227)	12,655	3,982
Net cash provided by operating activities	62,817	80,639	71,429
Proceeds from sale of available-for-sale securities	0	55,000	56,169
Net cash provided by (used in) investing activities	81,379	(198,730)	(196,195)
Preferred Stock, Redemption Amount	0	0	(57,943)
Redemption of Trust Preferred Securities	0	0	(3,885)
Net cash provided by (used in) financing activities	(181,712)	198,677	105,302
Statements of Cash Flows | Parent Company
Cash, Period Increase (Decrease)	4,261	17,707	(44,827)
Cash beginning of period	37,716	20,009	64,836
Cash end of period	41,977	37,716	20,009
Statements of Cash Flows | Parent Company | Additional Cash Payment Information
Interest Paid	5,059	846	730
Statements of Cash Flows | Parent Company | Operating Activities
Operating Activity Net Income Parent Company	51,564	45,342	46,502
Net cash provided by operating activities	13,908	10,776	25,913
Statements of Cash Flows | Parent Company | Operating Activities | Items not requiring (providing) cash
Increase (Decrease) Equity in Undistributed Earnings of Subsidiaries	(38,684)	(34,067)	(19,850)
Compensation expense for stock option grants	564	483	382
Gain on Redemption of Trust Preferred Securities	0	0	(1,115)
Net realized gains on sales of non-marketable securities	0	0	(301)
Net realized gains on sales of available-for-sale securities	0	(2,735)	0
Statements of Cash Flows | Parent Company | Operating Activities | Changes in
Prepaid expenses and other assets	132	175	(27)
Accounts Payable and Other Accrued Liabilities	(115)	1,495	63
Income taxes parent	6	(206)	55
Statements of Cash Flows | Parent Company | Investing Activities
Proceeds from sale of available-for-sale securities	0	3,583	0
Investment in Subsidiary	0	(60,000)	0
Investment/Return of principal - other investments	0	(2)	16
Net cash provided by (used in) investing activities	0	(56,419)	16
Statements of Cash Flows | Parent Company | Financing Activities
Payments for Derivative Instrument, Financing Activities	0	73,472	0
Preferred Stock, Redemption Amount	0	0	(57,943)
Redemption of Trust Preferred Securities	0	0	(3,885)
Payments for Repurchase of Warrants	0	0	0
Dividends, Paid-in-kind	(12,894)	(12,232)	(12,290)
Stock options excercised	3,247	2,110	3,362
Net cash provided by (used in) financing activities	$ (9,647)	$ 63,350	$ (70,756)