Loans and Allowance for Loan Losses - Schedule of Loans Modified and Considered Troubled Debt Restructuring (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014 SecurityLoan	Jun. 30, 2013 SecurityLoan	Jun. 30, 2014 SecurityLoan	Jun. 30, 2013 SecurityLoan
Troubled Debt Restructured Loan Modifications by Class [Line Items]
Number	5	6	13	13
Pre-Modification Recorded Investment	$ 855	$ 3,117	$ 1,039	$ 4,058
Post-Modification Recorded Investment	855	3,117	1,039	4,058
Agricultural [Member]
Troubled Debt Restructured Loan Modifications by Class [Line Items]
Number	1		1	1
Pre-Modification Recorded Investment	39		39	24
Post-Modification Recorded Investment	39		39	24
Real Estate [Member]
Troubled Debt Restructured Loan Modifications by Class [Line Items]
Number	3	4	4	8
Pre-Modification Recorded Investment	514	2,982	590	3,779
Post-Modification Recorded Investment	514	2,982	590	3,779
Commercial [Member]
Troubled Debt Restructured Loan Modifications by Class [Line Items]
Number	1	1	5	3
Pre-Modification Recorded Investment	302	98	399	218
Post-Modification Recorded Investment	302	98	399	218
Consumer [Member]
Troubled Debt Restructured Loan Modifications by Class [Line Items]
Number		1	3	1
Pre-Modification Recorded Investment		37	11	37
Post-Modification Recorded Investment		$ 37	$ 11	$ 37