Contractual Maturity Information for Securities Held to Maturity (Detail) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Investments Debt And Equity Securities [Abstract]
Due in 1 year or less, Amortized Cost	$ 1,466
Due after 1 year through 5 years, Amortized Cost	30,829
Due after 5 years through 10 years, Amortized Cost	31,884
Due after 10 years, Amortized Cost	65,319
Total securities held to maturity, Amortized Cost	129,498	114,756
Due in 1 year or less, Fair Value	1,614
Due after 1 year through 5 years, Fair Value	33,932
Due after 5 years through 10 years, Fair Value	35,092
Due after 10 years, Fair Value	71,893
Held to Maturity, Fair value	$ 142,531	$ 129,495

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

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