Investment Securities - Summary of Securities in Other Assets, at Cost (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
Schedule of Investments [Line Items]
Total equity securities	$ 6,552	$ 6,738
FHLB stock [Member]
Schedule of Investments [Line Items]
Total equity securities	1,099	2,938
First National Bankers Bankshares, Inc. (FNBB) stock [Member]
Schedule of Investments [Line Items]
Total equity securities	600	600
Other investments [Member]
Schedule of Investments [Line Items]
Total equity securities	$ 4,853	$ 3,200