PARENT COMPANY ONLY FINANCIAL INFORMATION - Condensed Statements of Cash Flows (Details) - USD ($)
$ in Thousands
 3 Months Ended 12 Months Ended
Dec. 31, 2016
Sep. 30, 2016
Jun. 30, 2016
Mar. 31, 2016
Dec. 31, 2015
Sep. 30, 2015
Jun. 30, 2015
Mar. 31, 2015
Dec. 31, 2016
Dec. 31, 2015
Dec. 31, 2014
Cash flows from operating activities:                      
Net income $ 11,580 $ 8,045 $ 6,790 $ 5,118 $ 7,696 $ 3,451 $ 6,670 $ 6,590 $ 31,533 $ 24,407 $ 10,816
Adjustments to reconcile net income to net cash provided by operating activities:                      
Amortization of restricted stock awards                 555 517 468
Compensation expense for stock option grants                 492 413 240
Change in other assets                 (6,399) (2,774) 1,797
Change in other liabilities                 (175) (648) 1,391
Net cash provided by operating activities                 25,543 73,645 21,498
Cash flows from investing activities:                      
Net cash paid in acquisitions                 5,191 20,053 (85,021)
Net cash (used in) provided by investing activities                 (360,350) (229,458) 30,092
Cash flows from financing activities:                      
Payments made on subordinated debt                 (8,000)    
Proceeds from issuance of subordinated debt, net of issuance costs                   55,325  
Proceeds from other borrowings                     14,000
Payments made on other borrowings                   (14,177) (7,857)
Cash dividends paid on common stock                 (9,853) (7,692) (3,512)
Cash dividends paid on preferred stock                     (4,254)
Proceeds from issuance of common stock in initial public offering, net of issuance costs                 71,475    
Proceeds from issuance of common stock under employee benefit plans                 1,318 470 215
Net cash provided by (used in) financing activities                 313,048 208,385 21,590
Net increase (decrease) in cash                 (21,759) 52,572 73,180
Cash and cash equivalents:                      
Beginning of year       212,475       159,903 212,475 159,903 86,723
End of year 190,716       212,475       190,716 212,475 159,903
Supplemental disclosures of noncash investing and financing activities:                      
Issuance of common stock for preferred dividends                     2,903
Cash portion of merger consideration accrued for at year-end                     20,053
Private Placement                      
Supplemental disclosures of noncash investing and financing activities:                      
Issuance of common stock                     16,156
Series C preferred stock                      
Supplemental disclosures of noncash investing and financing activities:                      
Conversion of preferred stock into common stock                     23,600
Series D preferred stock                      
Supplemental disclosures of noncash investing and financing activities:                      
Conversion of preferred stock into common stock                     22,470
Series E preferred stock                      
Supplemental disclosures of noncash investing and financing activities:                      
Conversion of preferred stock into common stock                     6,300
Series F preferred stock                      
Supplemental disclosures of noncash investing and financing activities:                      
Conversion of preferred stock into common stock                     5,000
Midland States Bancorp, Inc                      
Cash flows from operating activities:                      
Net income                 31,542 24,324 10,816
Adjustments to reconcile net income to net cash provided by operating activities:                      
Equity in undistributed income of subsidiary                 (36,256) (11,760) 1,403
Amortization of restricted stock awards                 555 517 468
Compensation expense for stock option grants                 492 413 240
Change in other assets                 4,237 (3,559) 576
Change in other liabilities                 225 (8,426) (1,065)
Net cash provided by operating activities                 795 1,509 12,438
Cash flows from investing activities:                      
Net cash paid in acquisitions                   (20,053) 1,500
Capital injection to subsidiaries                 (25,250) (30,000)  
Net cash (used in) provided by investing activities                 (25,250) (50,053) 1,500
Cash flows from financing activities:                      
Payments made on subordinated debt                 (8,000)    
Proceeds from issuance of subordinated debt, net of issuance costs                   55,325  
Proceeds from other borrowings                     14,000
Payments made on other borrowings                   (14,000) (15,938)
Cash dividends paid on common stock                 (9,853) (7,692) (3,512)
Cash dividends paid on preferred stock                     (4,254)
Proceeds from issuance of common stock in initial public offering, net of issuance costs                 (71,475)    
Proceeds from issuance of common stock under employee benefit plans                 1,318 470 215
Net cash provided by (used in) financing activities                 54,940 34,103 (9,489)
Net increase (decrease) in cash                 30,485 (14,441) 4,449
Cash and cash equivalents:                      
Beginning of year       $ 8,318       $ 22,759 8,318 22,759 18,310
End of year $ 38,803       $ 8,318       $ 38,803 $ 8,318 22,759
Supplemental disclosures of noncash investing and financing activities:                      
Issuance of common stock for preferred dividends                     2,903
Cash portion of merger consideration accrued for at year-end                     20,053
Midland States Bancorp, Inc | Private Placement                      
Supplemental disclosures of noncash investing and financing activities:                      
Issuance of common stock                     16,156
Midland States Bancorp, Inc | Series C preferred stock                      
Supplemental disclosures of noncash investing and financing activities:                      
Conversion of preferred stock into common stock                     23,600
Midland States Bancorp, Inc | Series D preferred stock                      
Supplemental disclosures of noncash investing and financing activities:                      
Conversion of preferred stock into common stock                     22,470
Midland States Bancorp, Inc | Series E preferred stock                      
Supplemental disclosures of noncash investing and financing activities:                      
Conversion of preferred stock into common stock                     6,300
Midland States Bancorp, Inc | Series F preferred stock                      
Supplemental disclosures of noncash investing and financing activities:                      
Conversion of preferred stock into common stock                     $ 5,000