Amortized Cost and Fair Value of Available-for-Sale and Held-to-Maturity Securities (Detail) (USD $) In Millions	Sep. 30, 2011		Dec. 31, 2010		Sep. 30, 2010
Debt securities:
Under 1 year	$ 898	[1]
1-5 years	11,387	[1]
5-10 years	1,768	[1]
Over 10 years	37	[1]
Other securities	1,337	[1]
Total	15,427		14,919		15,308
Debt securities:
Under 1 year	918	[1]
1-5 years	11,999	[1]
5-10 years	1,935	[1]
Over 10 years	35	[1]
Other securities	1,340	[1]
Fair Value	16,227	[2]	15,414	[2]	15,975	[2]
Debt securities:
Under 1 year	59	[1]
1-5 years	244	[1]
5-10 years	18	[1]
Over 10 years	16	[1]
Total	337	[3]	353	[3]	354	[3]
Debt securities:
Under 1 year	59	[1]
1-5 years	244	[1]
5-10 years	18	[1]
Over 10 years	16	[1]
Fair Value	$ 337		$ 353		$ 354

[1] Actual maturities may differ from contractual maturities when there exists a right to call or prepay obligations with or without call or prepayment penalties.

[2] Amortized cost of $15,427, $14,919 and $15,308 at September 30, 2011, December 31, 2010 and September 30, 2010, respectively.

[3] Fair value of $337, $353 and $354 at September 30, 2011, December 31, 2010 and September 30, 2010, respectively.