Amortized Cost and Fair Value of Available-for-Sale and Held-to-Maturity Securities (Detail) - USD ($) $ in Millions		Dec. 31, 2015	Dec. 31, 2014
Available-for-sale and other debt securities:
Less than 1 year	[1]	$ 695
1-5 years	[1]	7,277
5-10 years	[1]	18,191
Over 10 years	[1]	1,812
Equity securities		703
Available-for-sale and other securities, Amortized Cost		28,678	$ 21,677
Available-for-sale and other debt securities:
Less than 1 year	[1]	707
1-5 years	[1]	7,441
5-10 years	[1]	18,372
Over 10 years	[1]	1,821
Equity securities		703
Available-for-sale and other securities, fair value	[2]	29,044	22,408
Held-to-maturity debt securities:
Less than 1 year	[1]	43
1-5 years	[1]	12
5-10 years	[1]	13
Over 10 years	[1]	2
Held-to-maturity securities, amortized cost	[3]	70	187
Held-to-maturity debt securities:
Less than 1 year	[1]	43
1-5 years	[1]	12
5-10 years	[1]	13
Over 10 years	[1]	2
Held-to-maturity securities, fair value		$ 70	$ 187

[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 $28,678 and $21,677 at December 31, 2015 and 2014, respectively.

[3] Fair value of $70 and $187 at December 31, 2015 and 2014, respectively.