Securities - Additional Information (Detail) (USD $)	9 Months Ended
Sep. 30, 2012	Sep. 30, 2011	Dec. 31, 2011
Schedule of Trading Securities and Other Trading Assets [Line Items]
Proceeds from sales of securities available for sale	$ 991,842,000	$ 991,014,000
Gross realized gains from securities	20,300,000	16,000,000
Gross realized losses from securities	342,000	70,000
Unrealized gains on trading securities	416,700	193,500
Pledged securities for deposits	$ 4,500,000,000		$ 5,400,000,000

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

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Reference 6: http://www.xbrl.org/2003/role/presentationRef

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+ Details

- Definition

The increase (decrease) resulting in a gain from the difference between the fair value and the carrying value, or in the comparative fair values, of trading securities held at each balance sheet date, that was included in earnings for the period.

+ References

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+ Details