Investment Securities - Investments' Gross Unrealized Losses and Fair Value (Detail) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014
Available For Sale And Held To Maturity Securities In Continuous Unrealized Loss Position [Line Items]
Available-for-Sale, Less than 12 Months, Fair Value	$ 60,725	$ 45,876
Available-for-Sale, Less than 12 Months, Unrealized Losses	(326)	(138)
Available-for-Sale, 12 Months or More, Fair Value	8,459	12,914
Available-for-Sale, 12 Months or More, Unrealized Losses	(140)	(241)
Held-to-Maturity, Less than 12 Months, Fair Value	17,697	538
Held-to-Maturity, Less than 12 Months, Unrealized Losses	(87)	(2)
Held-to-Maturity, 12 Months or More, Fair Value	1,673	11,664
Held-to-Maturity, 12 Months or More, Unrealized Losses	(42)	(52)
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	31,006	24,459
Available-for-Sale, Less than 12 Months, Unrealized Losses	(99)	(67)
Available-for-Sale, 12 Months or More, Fair Value	7,203	7,630
Available-for-Sale, 12 Months or More, Unrealized Losses	(125)	(125)
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	28,923	19,069
Available-for-Sale, Less than 12 Months, Unrealized Losses	(225)	(70)
Available-for-Sale, 12 Months or More, Fair Value	1,256	1,304
Available-for-Sale, 12 Months or More, Unrealized Losses	(15)	(23)
Held-to-Maturity, Less than 12 Months, Fair Value	13,740	538
Held-to-Maturity, Less than 12 Months, Unrealized Losses	(74)	(2)
Corporate notes [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	796
Available-for-Sale, Less than 12 Months, Unrealized Losses	(2)
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	3,957
Held-to-Maturity, Less than 12 Months, Unrealized Losses	(13)
Held-to-Maturity, 12 Months or More, Fair Value	1,673	11,664
Held-to-Maturity, 12 Months or More, Unrealized Losses	(42)	(52)
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
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
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.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 320

-SubTopic 10

-Section 50

-Paragraph 7

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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.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 320

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-Section 50

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

-Publisher FASB

-Name Accounting Standards Codification

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-URI http://asc.fasb.org/extlink&oid=27724398&loc=d3e27337-111563

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-Publisher FASB

-Name Accounting Standards Codification

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

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This item represents the fair value of securities categorized as held-to-maturity that have been in a continuous unrealized loss position for less than twelve months.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 320

-SubTopic 10

-Section 50

-Paragraph 7

-URI http://asc.fasb.org/extlink&oid=27724398&loc=d3e27337-111563

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

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This item represents the fair value of securities categorized as held-to-maturity securities that have been in a continuous unrealized loss position for twelve months or longer.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 320

-SubTopic 10

-Section 50

-Paragraph 7

-URI http://asc.fasb.org/extlink&oid=27724398&loc=d3e27337-111563

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 320

-SubTopic 10

-Section 50

-Paragraph 6

-Subparagraph (a)(1)

-URI http://asc.fasb.org/extlink&oid=27724398&loc=d3e27290-111563

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