Stockholders' Equity (Stock Rollforward) (Details) - shares	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Increase (Decrease) in Stock by Class
Common stock, shares issued, beginning of period	15,426,973
Treasury stock, shares, beginning of period	590,246
Changes related to deferred compensation plan:
Purchase of treasury stock	0
Changes related to private placement:
Common stock, shares issued, end of period	18,931,200	15,426,973
Treasury stock, shares, end of period	586,688	590,246
Common Stock
Class of Stock
Stock Issued During Period, Shares, Restricted Stock Award, Gross	131,011	101,926	83,206
Increase (Decrease) in Stock by Class
Common stock, shares issued, beginning of period	15,599,643	11,352,036	11,252,244
Changes related to stock-based compensation awards:
Stock Issued During Period, Shares, Restricted Stock Award, Forfeited	(28,219)	(6,062)	(3,096)
Stock Issued During Period, Shares, Share-based Compensation, Gross	(2,810)	(100)
Changes related to dividend reinvestment plan:
Common shares issued under dividend reinvestment plan	18,257	17,230	19,682
Changes related to private placement:
Common stock, shares issued, end of period	18,931,200	15,599,643	11,352,036
Treasury Stock
Increase (Decrease) in Stock by Class
Treasury stock, shares, beginning of period	590,246	600,794	607,688
Changes related to stock-based compensation awards:
Release of restricted common shares	25,205	18,031	6,862
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period		(2,792)
Stock Issued During Period, Shares, Share-based Compensation, Gross	(100)
Reissuance of treasury stock for common stock awards		(12,030)
Changes related to deferred compensation plan:
Purchase of treasury stock	7,654	4,236	3,652
Reissuance of treasury stock	(9,642)	(9,390)	(9,147)
Changes related to Board Compensation:
Common shares issued under compensation plan for Board of Directors	(10,231)	(8,603)	(8,261)
Stock Issued During Period, Shares, Employee Stock Purchase Plans	(16,446)
Changes related to private placement:
Treasury stock, shares, end of period	586,686	590,246	600,794
NB&T Financial Group, Inc. [Member] | Common Stock
Changes related to stock issued in acquisitions:
Stock Issued During Period, Shares, Acquisitions	3,207,698
NB&T Financial Group, Inc. [Member] | Common Stock
Changes related to stock issued in acquisitions:
Stock Issued During Period, Shares, Acquisitions	3,207,698
Midwest Bancshares, Inc. | Common Stock
Changes related to stock issued in acquisitions:
Stock Issued During Period, Shares, Acquisitions		256,282
Ohio Heritage Bancorp, Inc. | Common Stock
Changes related to stock issued in acquisitions:
Stock Issued During Period, Shares, Acquisitions		1,364,735
North Akron Savings Bank | Common Stock
Changes related to stock issued in acquisitions:
Stock Issued During Period, Shares, Acquisitions		665,570
Private Placement [Member] | Common Stock
Changes related to private placement:
Issuance of Private Placement		1,847,826
Private Placement [Member] | Common Stock
Changes related to private placement:
Issuance of Private Placement	1,847,826