Acquisitions and Divestitures - Narrative (Details) $ / shares in Units, shares in Millions			9 Months Ended
	Dec. 31, 2015 USD ($) bank shares	Apr. 17, 2015 USD ($) bank $ / shares	Sep. 30, 2016 USD ($)	Sep. 30, 2015 USD ($)
Business Acquisition [Line Items]
Common stock issued, value
Ameriana
Business Acquisition [Line Items]
Percentage of interest acquired	100.00%
Number of banking centers acquired | bank	13
Stock issued as a part of acquisition (in shares) | shares	2.8
Common stock issued, value	$ 70,400,000
Core deposit intangible	$ 5,342,000
Acquired intangible asset, expected useful life	10 years
Purchase price	$ 70,402,000
Ameriana | Common Stock
Business Acquisition [Line Items]
Number of shares of common stock	0.9037
C Financial
Business Acquisition [Line Items]
Percentage of interest acquired		100.00%
Number of banking centers acquired | bank		6
Core deposit intangible		$ 981,000
Acquired intangible asset, expected useful life		10 years
Purchase price		$ 14,500,000
Cash received by shareholders for each share of common stock held (in dollars per share) | $ / shares		$ 6.738
Goodwill, expected tax deductible period		15 years