Loans (Additional Information) (Details)	3 Months Ended
	Mar. 31, 2016 USD ($) loan	Mar. 31, 2015 USD ($) loan	Dec. 31, 2015 USD ($)
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans acquired, net of purchase discount	$ 1,899,787,000		$ 1,549,909,000
Number of loans modified as troubled debt restructurings | loan	0	0
Increase (decrease) in allowance for loan losses	$ 0	$ 0
Charge-offs due to troubled debt restructurings	0	0
Additional lending amount to customers whose loan terms has been modified in troubled debt restructuring	0		0
Carrying amount of consumer mortgage loans secured by residential real estate properties	154,000		$ 169,000
Troubled Debt Restructuring that Subsequently Defaulted
Accounts, Notes, Loans and Financing Receivable [Line Items]
Charge-offs due to troubled debt restructurings	0	0
Increase (decrease) in allowance for loan losses	0	$ 0
Loans Purchased
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loan losses reversed	0
River Valley Bancorp
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans acquired, net of purchase discount	316,564,000
Purchase discount on loans acquired	$ 10,572,000