The amount of other than temporary impairment (OTTI) losses on equity securities, OTTI related to credit losses on debt securities, and OTTI losses on debt securities when the entity intends to sell the securities or it is more likely than not that the entity will be required to sell the securities before recovery of its amortized cost basis. Additionally, this item includes OTTI losses recognized during the period on investments accounted for under the cost method of accounting.

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The amount of other than temporary impairment losses on investments in debt and equity securities categorized as Available-for-sale which have been recognized in earnings during the period. Such impairment losses consist of other than temporary impairments (OTTI) on equity securities, credit losses on investments in debt securities, and when the entity intends to sell an impaired debt security or it is more likely than not that the entity will be required to sell the impaired debt security before recovery of its amortized cost basis.

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- Definition

The amount of other than temporary impairment losses on investments in debt securities categorized as Held-to-maturity which have been recognized in earnings during the period. Such impairment losses consist of other than temporary impairments (OTTI) of investments in debt securities due to credit losses and other than temporary impairments due to other than credit losses when the entity intends to sell an impaired debt security or it is more likely than not that the entity will be required to sell the impaired debt security before recovery of its amortized cost basis.

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Investment Securities - Other-Than-Temporary Impairment Losses on Securities Recognized in Earnings (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended				12 Months Ended
	Sep. 30, 2012	Jun. 30, 2012	Dec. 31, 2011	Mar. 31, 2011	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Other than Temporary Impairment, Credit Losses Recognized in Earnings [Line Items]
Net impairment losses on securities recognized in earnings	$ (4,697)	$ (550)	$ (19,143)	$ (825)	$ 5,247	$ 19,968	$ 4,642
Held-to-maturity Securities [Member] \| Trust preferred securities [Member]
Other than Temporary Impairment, Credit Losses Recognized in Earnings [Line Items]
Net impairment losses on securities recognized in earnings						18,314
Available For Sale Securities [Member] \| Trust preferred securities [Member]
Other than Temporary Impairment, Credit Losses Recognized in Earnings [Line Items]
Net impairment losses on securities recognized in earnings					4,525	825	2,377
Available For Sale Securities [Member] \| Residential mortgage-backed securities [Member]
Other than Temporary Impairment, Credit Losses Recognized in Earnings [Line Items]
Net impairment losses on securities recognized in earnings					$ 722	$ 829	$ 2,265