Other Intangibles - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Jul. 14, 2017	May 19, 2017
Business Acquisition [Line Items]
Measurement period adjustment			$ 2,142
Intangible asset amortization		$ 5,647	$ 3,910	$ 2,835
IAB
Business Acquisition [Line Items]
Core deposit intangible					$ 17,403
Arlington Bank
Business Acquisition [Line Items]
Core deposit intangible						$ 4,526
Merger with Ameriana Bancorp
Business Acquisition [Line Items]
Measurement period adjustment	$ 2,142
Core deposits | IAB
Business Acquisition [Line Items]
Core deposit intangible					13,638
Core deposits | Arlington Bank
Business Acquisition [Line Items]
Core deposit intangible						$ 4,526
Core deposits | Merger with Ameriana Bancorp
Business Acquisition [Line Items]
Core deposit intangible				$ 5,342
Noncompete agreements | IAB
Business Acquisition [Line Items]
Core deposit intangible					$ 3,765