Fair Value of Financial Assets and Liabilities Contractual Maturities of Investments (Detail) (Debt Securities, USD $) In Millions, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
Debt Securities
Amortized Cost Basis
Due within one year	$ 3,439
Due after 1 year through 5 years	5,707
Due after 5 years through 10 years	539
Due after 10 years	505
Available For Sale Securities Amortized Cost	10,190	6,535
Aggregate Fair Value
Due within one year	3,442
Due after 1 year through 5 years	5,718
Due after 5 years through 10 years	546
Due after 10 years	499
Available For Sale Securities Fair Value	$ 10,205	$ 6,595

Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading.

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