Business Combinations, Goodwill and Intangible Assets (Fair Value of Assets and Liabilities Acquired) (Details) - USD ($) $ in Thousands	Mar. 01, 2016	Feb. 29, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Recognized Amounts of Identifiable Assets Acquired and Liabilities Assumed:
Goodwill			$ 54,058	$ 54,058	$ 20,536	$ 20,536
River Valley Bancorp
Consideration
Cash for Options and Fractional Shares	$ 395	$ 395
Cash Consideration	24,975	$ 24,975
Equity Instruments	62,022
Fair Value of Total Consideration Transferred	87,392
Recognized Amounts of Identifiable Assets Acquired and Liabilities Assumed:
Cash	17,877
Federal Funds Sold and Other Short-term Investments	6,477
Interest-bearing Time Deposits with Banks	992
Securities	132,396
Loans	317,760
Stock in FHLB of Indianapolis and Other Restricted Stock, at Cost	3,127
Premises, Furniture & Equipment	9,650
Other Real Estate	882
Intangible Assets	2,613
Company Owned Life Insurance	12,842
Accrued Interest Receivable and Other Assets	9,139
Deposits - Non-interest Bearing	(9,584)
Deposits - Interest Bearing	(395,862)
FHLB Advances and Other Borrowings	(49,910)
Accrued Interest Payable and Other Liabilities	(4,529)
Total Identifiable Net Assets	53,870
Goodwill	$ 33,522