Investment Securities - Investments' Gross Unrealized Losses and Fair Value (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Available For Sale And Held To Maturity Securities In Continuous Unrealized Loss Position [Line Items]
Available-for-Sale, Less than 12 Months, Fair Value	$ 45,876	$ 69,120
Available-for-Sale, Less than 12 Months, Unrealized Losses	(138)	(1,558)
Available-for-Sale, 12 Months or More, Fair Value	12,914	271
Available-for-Sale, 12 Months or More, Unrealized Losses	(241)	(18)
Held-to-Maturity, Less than 12 Months, Fair Value	538
Held-to-Maturity, Less than 12 Months, Unrealized Losses	(2)
Held-to-Maturity, 12 Months or More, Fair Value	11,664
Held-to-Maturity, 12 Months or More, Unrealized Losses	(52)
Obligations of U.S. Government Sponsored Agencies [Member]
Available For Sale And Held To Maturity Securities In Continuous Unrealized Loss Position [Line Items]
Available-for-Sale, Less than 12 Months, Fair Value	1,999
Available-for-Sale, Less than 12 Months, Unrealized Losses	(1)
Held-to-Maturity, Less than 12 Months, Fair Value		33,365
Held-to-Maturity, Less than 12 Months, Unrealized Losses		(1,685)
Held-to-Maturity, 12 Months or More, Fair Value	11,664
Held-to-Maturity, 12 Months or More, Unrealized Losses	(52)
Commercial [Member]
Available For Sale And Held To Maturity Securities In Continuous Unrealized Loss Position [Line Items]
Available-for-Sale, Less than 12 Months, Fair Value	19,069	21,231
Available-for-Sale, Less than 12 Months, Unrealized Losses	(70)	(337)
Available-for-Sale, 12 Months or More, Fair Value	1,304	271
Available-for-Sale, 12 Months or More, Unrealized Losses	(23)	(18)
Held-to-Maturity, Less than 12 Months, Fair Value	538
Held-to-Maturity, Less than 12 Months, Unrealized Losses	(2)
Residential [Member]
Available For Sale And Held To Maturity Securities In Continuous Unrealized Loss Position [Line Items]
Available-for-Sale, Less than 12 Months, Fair Value	24,459	43,091
Available-for-Sale, Less than 12 Months, Unrealized Losses	(67)	(885)
Available-for-Sale, 12 Months or More, Fair Value	7,630
Available-for-Sale, 12 Months or More, Unrealized Losses	(125)
Obligations of States and Political Subdivisions [Member]
Available For Sale And Held To Maturity Securities In Continuous Unrealized Loss Position [Line Items]
Available-for-Sale, Less than 12 Months, Fair Value	269	1,050
Available-for-Sale, Less than 12 Months, Unrealized Losses		(2)
U.S. Treasury Securities [Member]
Available For Sale And Held To Maturity Securities In Continuous Unrealized Loss Position [Line Items]
Available-for-Sale, Less than 12 Months, Fair Value	80	3,748
Available-for-Sale, Less than 12 Months, Unrealized Losses		(334)
Available-for-Sale, 12 Months or More, Fair Value	3,980
Available-for-Sale, 12 Months or More, Unrealized Losses	$ (93)

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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 twelve months or longer.

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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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This item represents the aggregate fair value of investments in debt and equity securities categorized neither as held-to-maturity nor trading securities that have been in a continuous unrealized loss position for less than twelve months.

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Amount of accumulated unrealized loss on investments in debt securities classified as held-to-maturity that have been in a continuous loss position for twelve months or longer.

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

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