Loans and Allowance for Loan Losses - Loans Held-for-Investment by Class of Financing Receivables (Detail) - USD ($) $ in Thousands	Jun. 30, 2016	Dec. 31, 2015	Jun. 30, 2015
Loans [Line Items]
Total	$ 3,283,655	$ 3,317,050	$ 2,942,224
Commercial [Member]
Loans [Line Items]
Total	661,659	696,163	649,909
Agriculture [Member]
Loans [Line Items]
Total	80,812	102,351	92,317
Real Estate [Member]
Loans [Line Items]
Total	2,154,388	2,136,233	1,838,488
Consumer [Member]
Loans [Line Items]
Total	$ 386,796	$ 382,303	$ 361,510

Amount before allowance of loans and leases held in portfolio, including but not limited to, commercial and consumer loans. Includes deferred interest and fees, undisbursed portion of loan balance, unamortized costs and premiums and discounts from face amounts. Excludes loans and leases covered under loss sharing agreements.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=65884687&loc=d3e4428-111522

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant