Loans - (Summary of Company's Carrying Value of Non-Accrual TDR's) (Detail) - Non-Accruing TDR [Member] - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Loans [Line Items]
Carrying Value of Non - Accruing TDR's	$ 17,793	$ 6,973
Commercial [Member]
Loans [Line Items]
Carrying Value of Non - Accruing TDR's	15,897	3,994
Agriculture [Member]
Loans [Line Items]
Carrying Value of Non - Accruing TDR's	81	365
Commercial Real Estate [Member]
Loans [Line Items]
Carrying Value of Non - Accruing TDR's	1,135	458
Residential Real Estate Segment [Member]
Loans [Line Items]
Carrying Value of Non - Accruing TDR's	678	1,966
Consumer [Member]
Loans [Line Items]
Carrying Value of Non - Accruing TDR's	$ 2	$ 190