Investment Securities Available for Sale - Additional Information (Detail) (USD $)	12 Months Ended
Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Schedule of Available-for-sale Securities [Line Items]
Proceeds from the sale of investment securities available-for-sale	$ 262,443,000	$ 397,086,000	$ 3,825,313,000
Available-for-sale Securities
Schedule of Available-for-sale Securities [Line Items]
Realized gains (losses) on the sale of investment securities available-for-sale	8,400,000	3,700,000
Equity securities (without contractual maturity)
Schedule of Available-for-sale Securities [Line Items]
Other than Temporary Impairment Losses, Investments	$ 340,000	$ 264,000

The amount by which the fair value of an investment is less than the amortized cost basis or carrying amount of that investment at the balance sheet date and the decline in fair value is deemed to be other than temporary, before considering whether or not such amount is recognized in earnings or other comprehensive income.

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+ Details

- Definition

The cash inflow associated with the sale of debt and equity securities classified as available-for-sale securities.

+ References

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+ Details