Investment Securities - Investments' Gross Unrealized Losses and Fair Value (Detail) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
Available For Sale And Held To Maturity Securities In Continuous Unrealized Loss Position [Line Items]
Available-for-Sale, Less than 12 Months, Fair Value	$ 56,038	$ 1,253
Available-for-Sale, Less than 12 Months, Unrealized Losses	(1,339)	(3)
Available-for-Sale, 12 Months or More, Fair Value	296	5,617
Available-for-Sale, 12 Months or More, Unrealized Losses	(19)	(29)
U.S. Agencies [Member]
Available For Sale And Held To Maturity Securities In Continuous Unrealized Loss Position [Line Items]
Held-to-Maturity, Less than 12 Months, Fair Value	33,508	7,491
Held-to-Maturity, Less than 12 Months, Unrealized Losses	(1,600)	(7)
Held-to-Maturity, 12 Months or More, Fair Value
Held-to-Maturity, 12 Months or More, Unrealized Losses
Mortgage-Backed 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	50,328	1,173
Available-for-Sale, Less than 12 Months, Unrealized Losses	(996)	(3)
Available-for-Sale, 12 Months or More, Fair Value	296	5,617
Available-for-Sale, 12 Months or More, Unrealized Losses	(19)	(29)
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	3,766	80
Available-for-Sale, Less than 12 Months, Unrealized Losses	(318)
Available-for-Sale, 12 Months or More, Fair Value
Available-for-Sale, 12 Months or More, Unrealized Losses
Obligations of States, Counties 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	1,944
Available-for-Sale, Less than 12 Months, Unrealized Losses	(25)
Available-for-Sale, 12 Months or More, Fair Value
Available-for-Sale, 12 Months or More, Unrealized Losses

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Available for sale securities continuous unrealized loss position less than twelve months aggregate losses accumulated in investments.

+ References

No definition available.

+ Details

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- Definition

Available for sale securities continuous unrealized loss position twelve months or longer aggregate losses accumulated in investments.

+ References

No definition available.

+ Details

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- Definition

Held-to-maturity securities continuous unrealized loss position less than twelve months accumulated loss.

+ References

No definition available.

+ Details

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- Definition

Held-to-maturity securities, continuous unrealized loss position twelve months or longer accumulated loss.

+ References

No definition available.

+ Details

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- Definition

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

-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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- Definition

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

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- Definition

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

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