Securities - Amortized Cost, Fair Value and Carrying Amount of Securities Held to Maturity by Contractual Maturity (Detail) (USD $) In Millions, unless otherwise specified	Sep. 30, 2012	Dec. 31, 2011
Schedule of Held-to-maturity Securities [Line Items]
Due after one year through five years, Amortized cost	$ 157
Due after ten years, Amortized cost	1,041
Total securities held to maturity, Amortized cost	1,198
Due after one year through five years, Carrying Value	136
Due after ten years, Carrying Value	1,046
Total securities held to maturity, Carrying Value	1,182	1,273
Due after one year through five years, Fair Value	161
Due after ten years, Fair Value	1,063
Total securities held to maturity, Fair Value	$ 1,224	$ 1,429

Held to maturity securities debt maturities after one through five years amortized cost.

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- Definition

Held to maturity securities debt maturities after ten years amortized cost.

+ References

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- Definition

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 investments in debt securities categorized as held-to-maturity valued at amortized cost, excludes other than temporary impairment (OTTI).

+ References

No definition available.

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- Definition

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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- Definition

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 next fiscal year through the fifth fiscal year following the latest fiscal year.

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Amount of held-to-maturity debt securities at fair value maturing after 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 after the tenth fiscal year following the latest fiscal year.

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-Name FASB Staff Position (FSP)

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This item represents the aggregate fair value of investments in debt securities as of the balance sheet date and which are categorized as held-to-maturity.

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-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

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