Amortized Cost and Fair Value of Available-for-Sale and Held-to-Maturity Securities (Detail) (USD $) In Millions, unless otherwise specified	Dec. 31, 2011		Dec. 31, 2010
Debt securities:
Under 1 year	$ 884	[1]
1-5 years	10,599	[1]
5-10 years	1,351	[1]
Over 10 years	750	[1]
Other securities	1,030	[1]
Total	14,614		14,919
Debt securities:
Under 1 year	906	[1]
1-5 years	11,197	[1]
5-10 years	1,462	[1]
Over 10 years	765	[1]
Other securities	1,032	[1]
Fair Value	15,362	[2]	15,414	[2]
Debt securities:
Under 1 year	36	[1]
1-5 years	255	[1]
5-10 years	16	[1]
Over 10 years	15	[1]
Total	322	[3]	353	[3]
Debt securities:
Under 1 year	36	[1]
1-5 years	255	[1]
5-10 years	16	[1]
Over 10 years	15	[1]
Fair Value	$ 322		$ 353

[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 $14,614 and $14,919 at December 31, 2011 and 2010 respectively.

[3] Fair value of $322 and $353 at December 31, 2011 and 2010, respectively.