Loans and Allowance for Loan Losses - Schedule of How Loans Were Modified as Troubled Debt Restructured Loans (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Financing Receivable, Modifications [Line Items]
Troubled Debt Restructured Loans	$ 384	$ 414	$ 3,507	$ 566
Adjusted Interest Rate [Member]
Financing Receivable, Modifications [Line Items]
Troubled Debt Restructured Loans		257		257
Extended Maturity [Member]
Financing Receivable, Modifications [Line Items]
Troubled Debt Restructured Loans	2,605	206	2,605	206
Combined Rate and Maturity [Member]
Financing Receivable, Modifications [Line Items]
Troubled Debt Restructured Loans	902	103	902	103
Commercial [Member]
Financing Receivable, Modifications [Line Items]
Troubled Debt Restructured Loans	286	74	2,926	74
Commercial [Member] | Extended Maturity [Member]
Financing Receivable, Modifications [Line Items]
Troubled Debt Restructured Loans	2,449	74	2,449	74
Commercial [Member] | Combined Rate and Maturity [Member]
Financing Receivable, Modifications [Line Items]
Troubled Debt Restructured Loans	477		477
Agriculture [Member]
Financing Receivable, Modifications [Line Items]
Troubled Debt Restructured Loans				128
Agriculture [Member] | Extended Maturity [Member]
Financing Receivable, Modifications [Line Items]
Troubled Debt Restructured Loans		128		128
Real Estate [Member]
Financing Receivable, Modifications [Line Items]
Troubled Debt Restructured Loans		336	463	336
Real Estate [Member] | Adjusted Interest Rate [Member]
Financing Receivable, Modifications [Line Items]
Troubled Debt Restructured Loans		257		257
Real Estate [Member] | Extended Maturity [Member]
Financing Receivable, Modifications [Line Items]
Troubled Debt Restructured Loans	113		113
Real Estate [Member] | Combined Rate and Maturity [Member]
Financing Receivable, Modifications [Line Items]
Troubled Debt Restructured Loans	350	79	350	79
Consumer [Member]
Financing Receivable, Modifications [Line Items]
Troubled Debt Restructured Loans	98	4	118	28
Consumer [Member] | Extended Maturity [Member]
Financing Receivable, Modifications [Line Items]
Troubled Debt Restructured Loans	43	4	43	4
Consumer [Member] | Combined Rate and Maturity [Member]
Financing Receivable, Modifications [Line Items]
Troubled Debt Restructured Loans	$ 75	$ 24	$ 75	$ 24