Securities - Securities with Unrealized Losses Not Recognized in Income (Detail) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014
Schedule of Available-for-sale Securities [Line Items]
12 Months or less, Fair Value	$ 6,819	$ 20,806
12 Months or less, Unrealized Loss	(70)	(57)
More than 12 months, Fair Value	16,660	29,027
More than 12 months, Unrealized Loss	(229)	(552)
Total Fair Value	23,479	49,833
Total Unrealized Loss	(299)	(609)
U.S. Treasury Securities and Obligations of U.S. Government Agencies [Member]
Schedule of Available-for-sale Securities [Line Items]
12 Months or less, Fair Value	1,005	7,664
12 Months or less, Unrealized Loss	(1)	(17)
More than 12 months, Fair Value	4,884	11,888
More than 12 months, Unrealized Loss	(20)	(106)
Total Fair Value	5,889	19,552
Total Unrealized Loss	(21)	(123)
Obligations of States and Political Subdivisions [Member]
Schedule of Available-for-sale Securities [Line Items]
12 Months or less, Fair Value	5,487	853
12 Months or less, Unrealized Loss	(69)	(11)
More than 12 months, Fair Value	3,059	5,647
More than 12 months, Unrealized Loss	(150)	(295)
Total Fair Value	8,546	6,500
Total Unrealized Loss	(219)	(306)
Mortgage-backed Securities in Government Sponsored Entities [Member]
Schedule of Available-for-sale Securities [Line Items]
12 Months or less, Fair Value	327	12,289
12 Months or less, Unrealized Loss		(29)
More than 12 months, Fair Value	8,717	11,492
More than 12 months, Unrealized Loss	(59)	(151)
Total Fair Value	9,044	23,781
Total Unrealized Loss	$ (59)	$ (180)