Amortized Cost and Fair Value of Available-for-Sale and Held-to-Maturity Securities (Detail) (USD $) In Millions, unless otherwise specified	Dec. 31, 2013		Dec. 31, 2012
Debt securities:
Total	$ 18,409		$ 14,571
Debt securities:
Fair Value	18,597	[1]	15,207	[1]
Debt securities:
Total	208	[2]	284	[2]
Debt securities:
Fair Value	208		284
Available-for-sale Securities
Debt securities:
Under 1 year	120	[3]
1-5 years	3,703	[3]
5-10 years	9,765	[3]
Over 10 years	3,956	[3]
Other securities	865
Total	18,409		14,571
Debt securities:
Under 1 year	123	[3]
1-5 years	3,893	[3]
5-10 years	9,701	[3]
Over 10 years	4,011	[3]
Other securities	869
Fair Value	18,597		15,207
Held-to-maturity Securities
Debt securities:
Under 1 year	19	[3]
1-5 years	170	[3]
5-10 years	17	[3]
Over 10 years	2	[3]
Total	208		284
Debt securities:
Under 1 year	19	[3]
1-5 years	170	[3]
5-10 years	17	[3]
Over 10 years	2	[3]
Fair Value	$ 208		$ 284

[1] Amortized cost of $18,409 and $ 14,571 at December 31, 2013 and 2012, respectively.

[2] Fair value of $208 and $284 at December 31, 2013 and 2012, respectively.

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