Loans (Additional Information) (Details)	3 Months Ended		6 Months Ended
	Jun. 30, 2016 USD ($) loan	Jun. 30, 2015 USD ($) loan	Jun. 30, 2016 USD ($) loan	Jun. 30, 2015 USD ($) loan	Mar. 01, 2016 USD ($)	Dec. 31, 2015 USD ($)
Accounts, Notes, Loans and Financing Receivable [Line Items]
Acquired loans	$ 292,678,000		$ 292,678,000		$ 317,760,000
Loans acquired, net of purchase discount	$ 1,945,251,000		$ 1,945,251,000			$ 1,549,909,000
Number of loans modified as troubled debt restructurings | loan	0	0	0	0
Increase (decrease) in allowance for loan losses	$ 0	$ 0	$ 0	$ 0
Charge-offs due to troubled debt restructurings	0	0	0	0
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	376,000		376,000			$ 169,000
Troubled Debt Restructuring that Subsequently Defaulted
Accounts, Notes, Loans and Financing Receivable [Line Items]
Charge-offs due to troubled debt restructurings	0	95,000	0	95,000
Increase (decrease) in allowance for loan losses	0	0	0	0
Loans Purchased
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loan losses reversed	0	$ 44,000	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	301,826,000		301,826,000		328,431,000
Purchase discount on loans acquired	$ 9,148,000		$ 9,148,000		$ 10,671,000