Goodwill and Intangible Assets Reconciliation of Purchase Price to Goodwill (Details) - USD ($) $ in Thousands		9 Months Ended	12 Months Ended
	Sep. 08, 2016	Sep. 30, 2016	Dec. 31, 2015	Dec. 01, 2015	Aug. 14, 2015
Reconciliation of purchase price to goodwill recorded [Line Items]
Business Combination, Net Fair Value Adjustments	$ 8,044
Resulting goodwill from acquisition	16,785
First Clover Leaf [Member]
Reconciliation of purchase price to goodwill recorded [Line Items]
Purchase price (in excess of net book value)	8,741
Business Combination, Recognized Identifiable Assets and Liabilities Assumed, Securities	109,174
Business Combination, Recognized Identifiable Assets and Liabilities Assumed, Repossessed Assets	1,987
Fair value of premises and equipment	11,581
Fair value of time deposits	536,686
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, FHLB Advances	15,113
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Subordinated Debentures	3,269
Resulting goodwill from acquisition	16,800	$ 16,800
First Clover Leaf [Member] | Fair Value Adjustment [Member]
Reconciliation of purchase price to goodwill recorded [Line Items]
Business Combination, Recognized Identifiable Assets and Liabilities Assumed, Securities	737
Business Combination, Recognized Identifiable Assets and Liabilities Assumed, Loans, net	3,475
Business Combination, Recognized Identifiable Assets and Liabilities Assumed, Repossessed Assets	754
Fair value of premises and equipment	(1,963)
Fair value of time deposits	1,994
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, FHLB Advances	113
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Subordinated Debentures	(731)
Core deposit intangible	4,660
Other assets	$ 8,325
Illiana [Member]
Reconciliation of purchase price to goodwill recorded [Line Items]
Purchase price (in excess of net book value)				$ 2,807
Business Combination, Net Fair Value Adjustments				$ (1,827)
Resulting goodwill from acquisition			$ 980
OldNationalBankBranches [Member]
Reconciliation of purchase price to goodwill recorded [Line Items]
Purchase price (in excess of net book value)					$ 15,892
Fair value of premises and equipment					4,422
Fair value of time deposits			453,000		453,647
Business Combination, Net Fair Value Adjustments					(1,618)
Resulting goodwill from acquisition			$ 14,274
OldNationalBankBranches [Member] | Fair Value Adjustment [Member]
Reconciliation of purchase price to goodwill recorded [Line Items]
Fair value of premises and equipment					125
Fair value of time deposits					837
Core deposit intangible					$ (6,216)