Contractual Maturity Information for Securities Held to Maturity (Detail) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2012	Dec. 31, 2011
Schedule of Held-to-maturity Securities [Line Items]
Due in 1 year or less, Amortized Cost	$ 2,042
Due after 1 year through 5 years, Amortized Cost	24,846
Due after 5 years through 10 years, Amortized Cost	23,724
Due after 10 years, Amortized Cost	47,867
Total securities held to maturity, Amortized Cost	98,479	89,246
Due in 1 year or less, Fair Value	2,348
Due after 1 year through 5 years, Fair Value	28,565
Due after 5 years through 10 years, Fair Value	27,275
Due after 10 years, Fair Value	55,033
Held to Maturity, Fair value	$ 113,221	$ 102,287

For an unclassified balance sheet, this item represents investments in debt securities which are categorized as held-to-maturity. The held-to-maturity category is for those securities that the entity has the positive intent and ability to hold until maturity.

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Amount of held-to-maturity debt securities at fair value maturing in the sixth fiscal year through the tenth fiscal year following the latest fiscal year.

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Carrying amount of debt securities accounted for as held-to-maturity, net of adjustments including, but not limited to, accretion, amortization, collection of cash, previous other-than-temporary impairments (OTTI) recognized, and fair value hedge accounting adjustments, maturing in the fifth through tenth fiscal year following the latest fiscal year.

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