Consolidated Statements of Changes in Stockholders' Equity Consolidated Statements of Changes in Stockholders' Equity - USD ($) $ in Thousands	Total	Preferred Stock	Common Stock	Additional Paid-in Capital	Retained Earnings	Deferred Compensation	Accumulated Other Comprehensive Income (Loss)	Treasury Stock	First BancTrust [Member]	First BancTrust [Member] Preferred Stock	First BancTrust [Member] Common Stock	First BancTrust [Member] Additional Paid-in Capital	First BancTrust [Member] Retained Earnings	First BancTrust [Member] Deferred Compensation	First BancTrust [Member] Accumulated Other Comprehensive Income (Loss)	SCB Bancorp [Member]	SCB Bancorp [Member] Preferred Stock	SCB Bancorp [Member] Common Stock	SCB Bancorp [Member] Additional Paid-in Capital	SCB Bancorp [Member] Retained Earnings	SCB Bancorp [Member] Deferred Compensation	SCB Bancorp [Member] Accumulated Other Comprehensive Income (Loss)	First Clover Leaf [Member]	First Clover Leaf [Member] Preferred Stock	First Clover Leaf [Member] Common Stock	First Clover Leaf [Member] Additional Paid-in Capital	First Clover Leaf [Member] Retained Earnings	First Clover Leaf [Member] Deferred Compensation	First Clover Leaf [Member] Accumulated Other Comprehensive Income (Loss)	First Clover Leaf [Member] Treasury Stock
Balance at Dec. 31, 2015	$ 205,009	$ 27,400	$ 38,015	$ 79,626	$ 71,712	$ 3,245	$ 723	$ (15,712)
Net income	21,840				21,840
Other Comprehensive Income (Loss), Net of Tax	(6,484)						(6,484)
Dividends on preferred shares	(825)				(825)
Dividends on common stock	(6,511)				(6,511)
Issuance of common shares pursuant to the Dividend Reinvestment Plan	1,323		202	1,121
Issuance of common shares pursuant to the Deferred Compensation Plan	119		19	100
Issuance of common shares pursuant to the First Retirement & Savings Plan	14		2	12
Issuance of restricted common shares pursuant to the 2007 Stock Incentive Plan	80		12	68
Issuance of common shares pursuant to the exercise of stock options	62	0	10	52	0	0	0	0
Stock issued during period, Conversion of Preferred Shares	0	(27,400)	(5,421)	(21,979)	0	0	0	0
Stock Issued During Period, Value, Acquisitions																							$ 65,697	$ 0	$ 10,402	$ 55,295	$ 0	$ 0	$ 0	$ 0
Deferred Compensation	0					(25)		(25)
Tax benefit related to Deferred Compensation Plan distributions	140			140
Grant of restricted stock units pursuant to the 2007 Stock Incentive Plan	278			278
Vested restricted shares/units compensation expense	(69)	0	0	0	0	(69)	0	0
Balance at Dec. 31, 2016	280,673	0	54,083	158,671	86,216	3,201	(5,761)	(15,737)
Net income	26,684				26,684
Other Comprehensive Income (Loss), Net of Tax	3,525						3,525
Dividends on preferred shares	0
Reclassification from AOCI, Current Period, Tax	0		0	0	68	0	(68)	0
Dividends on common stock	(8,285)				(8,285)
Issuance of common shares pursuant to the Dividend Reinvestment Plan	1,057		120	937
Issuance of common shares pursuant to the Deferred Compensation Plan	232		28	204
Issuance of restricted common shares pursuant to the 2007 Stock Incentive Plan	1,804		189	1,615
Issuance of common shares pursuant to the exercise of stock options	699		110	589
Stock Issued During Period, Value, New Issues	3,251		395	2,856	0	0	0	0
Purchase of treasury shares	(797)							(797)
Deferred Compensation	0					(51)		(51)
Tax benefit related to Deferred Compensation Plan distributions	216			216
Adjustments to Additional Paid in Capital, Income Tax Benefit from Share-based Compensation	5		0	5	0	0	0	0
Adjustment to Additional Paid in Capital, Income Tax Effect from Share-based Compensation, Net	(1,849)		0	(1,849)	0	0	0	0
Grant of restricted stock units pursuant to the 2007 Stock Incentive Plan	359			359
Vested restricted shares/units compensation expense	390		0	0	0	390	0	0
Balance at Dec. 31, 2017	307,964		54,925	163,603	104,683	3,540	(2,304)	(16,483)
Net income	36,600				36,600
Other Comprehensive Income (Loss), Net of Tax	(4,169)						(4,169)
Dividends on preferred shares	0
Dividends on common stock	(9,891)				(9,891)
Issuance of common shares pursuant to the Dividend Reinvestment Plan	1,099		123	976
Issuance of common shares pursuant to the Deferred Compensation Plan	345		36	309
Issuance of restricted common shares pursuant to the 2007 Stock Incentive Plan	516		53	463
Issuance of common shares pursuant to the exercise of stock options	299		52	247
Stock Issued During Period, Value, Acquisitions									$ 61,222	$ 6,576	$ 54,646	$ 0	$ 0	$ 0	$ 0	$ 48,092	$ 5,322	$ 42,770	$ 0	$ 0	$ 0	$ 0
Stock Issued During Period, Value, New Issues	33,986	$ 3,789	30,197	0	0	0	0
Purchase of treasury shares	(138)							(138)
Deferred Compensation	0					(8)		(8)
Tax benefit related to Deferred Compensation Plan distributions	160			160
Grant of restricted stock units pursuant to the 2007 Stock Incentive Plan	566			566
Vested restricted shares/units compensation expense	(787)		0	0	0	(787)	0	0
Balance at Dec. 31, 2018	$ 475,864		$ 70,876	$ 293,937	$ 131,392	$ 2,761	$ (6,473)	$ (16,629)