Securities - Components of Held to Maturity Securities Portfolio (Detail) - USD ($)	Jun. 30, 2015	Dec. 31, 2014
Schedule Of Held To Maturity Securities [Line Items]
Held to maturity securities, Total amortized cost	$ 4,775,000	$ 0
Held to maturity securities, Gross unrecognized losses	(96,000)
Held to maturity securities, Fair value	4,679,000	$ 0
States of the U.S. and Political Subdivisions [Member]
Schedule Of Held To Maturity Securities [Line Items]
Held to maturity securities, Total amortized cost	4,775,000
Held to maturity securities, Gross unrecognized losses	(96,000)
Held to maturity securities, Fair value	$ 4,679,000

Amount after other than temporary impairment (OTTI) accretion, of investments in debt securities classified as held-to-maturity.

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Amount of accumulated unrealized loss on investments in debt securities classified as held-to-maturity.

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Fair value of investments in debt securities classified as held-to-maturity.

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