Securities - Gross Unrealized Losses and Fair Value of Company's Investments (Detail) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014
Schedule of Available-for-sale Securities [Line Items]
Fair Value less than 12 months	$ 31,846	$ 34,286
Fair value more than 12 months	75,270	90,657
Total fair value	107,116	124,943
Unrealized losses less than 12 months	(278)	(225)
Unrealized losses more than 12 months	(809)	(1,560)
Total unrealized losses	(1,087)	(1,785)
U.S. Treasury and Federal Agencies [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value less than 12 months		2,993
Fair value more than 12 months	16,937	20,762
Total fair value	16,937	23,755
Unrealized losses less than 12 months		(7)
Unrealized losses more than 12 months	(48)	(222)
Total unrealized losses	(48)	(229)
State and Municipal [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value less than 12 months	15,766	10,287
Fair value more than 12 months	1,259	2,050
Total fair value	17,025	12,337
Unrealized losses less than 12 months	(173)	(121)
Unrealized losses more than 12 months	(7)	(30)
Total unrealized losses	(180)	(151)
Federal Agency Collateralized Mortgage Obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value less than 12 months	9,233	15,013
Fair value more than 12 months	29,821	39,801
Total fair value	39,054	54,814
Unrealized losses less than 12 months	(21)	(88)
Unrealized losses more than 12 months	(516)	(957)
Total unrealized losses	(537)	(1,045)
Federal Agency Mortgage-backed Pools [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value less than 12 months	6,847	5,993
Fair value more than 12 months	27,253	28,044
Total fair value	34,100	34,037
Unrealized losses less than 12 months	(84)	(9)
Unrealized losses more than 12 months	(238)	(351)
Total unrealized losses	$ (322)	$ (360)

Amount of accumulated unrealized loss on investments in debt and equity securities classified as available-for-sale that have been in a continuous loss position for twelve months or longer.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

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-Section 50

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Amount of accumulated unrealized loss on investments in debt and equity securities classified as available-for-sale in a continuous loss position.

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This item represents the aggregate fair value of investments in debt and equity securities in an unrealized loss position which are categorized neither as held-to-maturity nor trading securities.

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Amount of accumulated unrealized loss on investments in debt and equity securities classified as available-for-sale that have been in a continuous loss position for less than twelve months.

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