Securities - Additional Information (Detail) (USD $)	12 Months Ended
Dec. 31, 2011	Dec. 31, 2012
Schedule Of Marketable Securities [Line Items]
Carrying value securities pledged as collateral	$ 58,200,000	$ 25,500,000
Number of securities sold	1
Amortized cost of security sold	295,000
Gain realized on sale of securities	7,000
Debt Securities
Schedule Of Marketable Securities [Line Items]
Fair Value of Investment in debt securities	$ 6,300,000	$ 3,000,000
Percentage of fair value of investment in debt	7.00%	8.00%

This item represents the gain (loss) realized on the sale of held-to-maturity securities disposed of during the period. Additionally, this item may include, if not separately presented, any losses recognized for other than temporary impairments (OTTI) of the subject investments in debt securities which are being or have been recognized in earnings during the period.

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This element represents the portion of the balance sheet assertion valued at fair value by the entity whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission. This item represents investment securities as of the balance sheet date which may include marketable securities, derivative financial instruments, and investments accounted for under the equity method.

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