Schedule of Contractual Maturities of Debt Securities Available for Sale (Detail) (USD $) In Millions, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Investments Classified by Contractual Maturity Date [Line Items]
Due within one year, Amortized Cost	$ 359
Due after one year through five years, Amortized Cost	1,826
Due after five years through ten years, Amortized Cost	2,946
Due after ten years, Amortized Cost	1,755
Mortgage and asset-backed securities, Amortized Cost	2,233
Total debt securities, Amortized Cost	9,119	8,928
Due within one year, Fair Value	362
Due after one year through five years, Fair Value	1,907
Due after five years through ten years, Fair Value	3,220
Due after ten years, Fair Value	1,994
Mortgage and asset-backed securities, Fair Value	2,364
Total debt securities, Fair Value	$ 9,847	$ 9,453

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This item represents the cost of debt and equity securities, which are categorized neither as held-to-maturity nor trading, net of adjustments including accretion, amortization, collection of cash, previous other-than-temporary impairments recognized in earnings (less any cumulative-effect adjustments recognized, as defined), and fair value hedge accounting adjustments, if any.

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