Loans and Allowance - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Apr. 17, 2015	Nov. 07, 2014	Nov. 12, 2013	Dec. 31, 2012
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for sale	$ 9,894				$ 7,235				$ 9,894	$ 7,235
Loans acquired through business combinations	430,289								430,289
Loans	4,693,822				3,924,865				4,693,822	3,924,865
Allowance for loan losses	62,453				63,964				62,453	63,964	$ 67,870				$ 69,366
Decrease in allowance for loan losses									1,511
Decrease in reserve on impaired loans									927
Reserve on impaired loans	$ 1,842				2,769				1,842	2,769	1,583
Net charge offs									1,928
Decrease in net charge offs									4,538
Provision for loan losses			$ 417		960	$ 1,600			417	2,560	6,648
Decrease in provision for loan losses									2,143
Commercial impaired loan total	$ 97,527				116,223				97,527	116,223	119,755
Merger with Ameriana Bancorp
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans acquired through business combinations	319,664								319,664
Commercial impaired loan total	11,365								11,365
Merger with C Financial Corporation
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans acquired through business combinations												$ 110,625
Commercial impaired loan total	1,841								1,841
Merger with Community Bancshares, Inc.
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans acquired through business combinations													$ 145,064
Commercial impaired loan total					17,027					17,027
Merger with CFS Bancorp, Inc.
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans acquired through business combinations														$ 603,114
Commercial impaired loan total											69,448
Other commercial loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	159,388				35,018				159,388	35,018
Increase in loans									124,370
Commercial and farmland
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	1,802,921				1,672,661				1,802,921	1,672,661
Reserve on impaired loans	392				1,120				$ 392	1,120	894
Percentage of troubled debt restructured loans									46.00%
Residential
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	786,105				647,315				$ 786,105	647,315
Allowance for loan losses	11,139				13,152				11,139	13,152	15,077				$ 14,157
Reserve on impaired loans	173				194				173	194	6
Provision for loan losses									310	(839)	3,514
Commercial and industrial loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	1,057,075				896,688				1,057,075	896,688
Reserve on impaired loans	$ 1,247				$ 1,055				$ 1,247	$ 1,055	$ 683
Percentage of troubled debt restructured loans									32.00%