Investment Securities - Schedule of Investment Portfolio (Detail) (USD $) In Millions, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
Amortized Cost And Fair Value Debt Securities [Abstract]
Securities available for sale, at fair value	$ 43,132	$ 63,979
Securities held to maturity, at carrying value	18,276	9
Total investments	$ 61,408	$ 63,988

Amount after other than temporary impairment (OTTI) accretion, of investments in debt securities classified as held-to-maturity.

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