Contractual Maturity of Available-for-sale Debt Securities (Detail) (USD $) In Millions, unless otherwise specified	Sep. 30, 2012
Amortized Cost
Due within one year	$ 674
Due after 1 year through 5 years	3,272
Due after 5 years through 10 years	0
Due after 10 years	7
Total	3,953
Fair Value
Due within one year	674
Due after 1 year through 5 years	3,276
Due after 5 years through 10 years	0
Due after 10 years	7
Total	$ 3,957

This item represents debt securities, at cost, net of adjustments including accretion, amortization, collection of cash, previous other-than-temporary impairments recognized in earnings (less any cumulative-effect adjustments, as defined), and fair value hedge accounting adjustments, if any, which are expected to mature after five years and through ten years from the balance sheet date and which are categorized neither as held-to-maturity nor trading securities.

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