Loans (Additional Information) (Details)	3 Months Ended		9 Months Ended
	Sep. 30, 2016 USD ($) loan	Sep. 30, 2015 USD ($) loan	Sep. 30, 2016 USD ($) loan	Sep. 30, 2015 USD ($) loan	Mar. 01, 2016 USD ($)	Dec. 31, 2015 USD ($)
Accounts, Notes, Loans and Financing Receivable [Line Items]
Acquired loans	$ 280,027,000		$ 280,027,000		$ 317,760,000
Loans acquired, net of purchase discount	$ 1,987,226,000		$ 1,987,226,000			$ 1,549,909,000
Number of loans modified as troubled debt restructurings | loan			0
Number of loans modified as troubled debt restructuring subsequently defaulted | loan	0	0	0	1
Recorded investment of loans modified as troubled debt restructuring that subsequently defaulted				$ 95
Additional lending amount to customers whose loan terms has been modified in troubled debt restructuring	$ 0		$ 0			0
Carrying amount of consumer mortgage loans secured by residential real estate properties	315,000		315,000			$ 169,000
Receivables Acquired with Deteriorated Credit Quality
Accounts, Notes, Loans and Financing Receivable [Line Items]
Increase in allowance for purchased loans	56	$ 0	56	0
Troubled Debt Restructuring that Subsequently Defaulted
Accounts, Notes, Loans and Financing Receivable [Line Items]
Charge-offs due to troubled debt restructurings				95,000
Increase (decrease) in allowance for loan losses				0
Loans Purchased
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loan losses reversed	0	$ 0	0	$ 44,000
River Valley Bancorp
Accounts, Notes, Loans and Financing Receivable [Line Items]
Acquired loans					317,760,000
Loans acquired, net of purchase discount	288,559,000		288,559,000		328,431,000
Purchase discount on loans acquired	$ 8,532,000		$ 8,532,000		$ 10,671,000