Fair Value Measurements and Disclosures - Changes in Fair Value of Other Real Estate (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Balance, end of year	$ 7,646	$ 9,630	$ 7,008
Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Balance, beginning of year	9,630	7,008	6,153
Loans transferred to ORE	1,345	4,537	2,576
Sales	(2,068)	(1,188)	(1,568)
Writedowns	(1,261)	(670)	(153)
Insurance proceeds from casualty loss		(57)
Balance, end of year	$ 7,646	$ 9,630	$ 7,008