Consolidated Statements of Changes in Stockholders' Equity Consolidated Statements of Changes in Stockholders' Equity (Parenthetical) - $ / shares	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Dividends on perferred stock (in dollars per share)	$ 0	$ 0	$ 150
Dividends on common stock (in dollars per share)	$ 0.70	$ 0.66	$ 0.62
Issuance of common shares pursuant to the Dividend Reinvestment Plan (in shares)	30,655	30,059	50,446
Issuance of common shares pursuant to the Deferred Compensation Plan (in shares)	9,043	6,875	4,683
Issuance of common shares pursuant to the First Retirement & Savings Plan (in shares)	0	0	558
Issuance of restricted common shares pursuant to the Stock Incentive Plan (in shares)	13,250	47,339	2,910
Stock issued during period, new issue (in shares)	0	98,710	0
Stock Issued During Period, Shares, Conversion of Convertible Securities	0	0	1,355,319
number of preferred shares converted to common shares	0	0	5,500
Purchase of treasury shares (in shares)	3,900	20,734	0
Issuance of common shares pursuant to the exercise of stock options (in shares)	10,500	27,500	2,500
Common Stock
Stock issued during period, new issue (in shares)	947,368	0	0
First Clover Leaf [Member]
Stock Issued During Period, Shares, Acquisitions	0	0	2,600,616
First BancTrust [Member]
Stock Issued During Period, Shares, Acquisitions	1,643,900	0	0
SCB Bancorp [Member]
Stock Issued During Period, Shares, Acquisitions	1,330,571	0	0