PARENT COMPANY ONLY FINANCIAL INFORMATION - Condensed Statements of Income (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Condensed Statements of Income
Interest expense	$ (9,196)	$ (10,334)	$ (11,559)	$ (14,663)	$ (15,757)	$ (15,556)	$ (14,559)	$ (13,831)	$ (45,752)	$ (59,703)	$ (43,280)
Income before income taxes	10,746	3,270	15,993	2,005	16,071	16,670	21,394	18,336	32,014	72,471	50,805
Income tax benefit	(2,413)	(3,184)	(3,424)	(456)	(3,279)	(4,015)	(5,039)	(4,354)	(9,477)	(16,687)	(11,384)
Net income	$ 8,333	$ 86	$ 12,569	$ 1,549	$ 12,792	$ 12,655	$ 16,355	$ 13,982	22,537	55,784	39,421
Midland States Bancorp, Inc
Condensed Statements of Income
Dividends from subsidiaries									89,890	43,900	17,000
Other income									0	0	6
Interest expense									(12,054)	(11,798)	(10,714)
Other expense									(1,309)	(2,753)	(1,180)
Income before income taxes									76,527	29,349	5,112
Income tax benefit									2,749	3,371	2,312
Income before equity in undistributed (loss) income of subsidiaries									79,276	32,720	7,424
Equity in undistributed (loss) income of subsidiaries									(56,739)	23,064	31,997
Net income									$ 22,537	$ 55,784	$ 39,421