Securities (Amortized Cost and Fair Value of Available-for-Sale and Held-to-Maturity Securities) (Detail) - USD ($) $ in Millions		Sep. 30, 2016	Dec. 31, 2015
Debt securities:
Less than 1 year	[1]	$ 1,011
1-5 years	[1]	12,264
5-10 years	[1]	13,556
Over 10 years	[1]	1,956
Equity securities		699
Available-for-sale and other securities, Amortized Cost		29,486	$ 28,678
Debt securities:
Less than 1 year	[1]	1,026
1-5 years	[1]	12,695
5-10 years	[1]	14,284
Over 10 years	[1]	1,983
Equity securities		701
Available-for-sale and other securities, fair value	[2]	30,689	29,044
Debt securities:
Less than 1 year	[1]	30
1-5 years	[1]	12
5-10 years	[1]	12
Over 10 years	[1]	2
Equity securities		0
Held-to-maturity securities, amortized cost	[3]	56	70
Debt securities:
Under 1 year	[1]	30
1-5 years	[1]	12
5-10 years	[1]	12
Over 10 years	[1]	2
Equity securities		0
Held-to-maturity securities, fair value		$ 56	$ 70

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

[2] Amortized cost of $ 29,486 and $ 28,678 at September 30, 2016 and Dec ember 31, 2015 , respectively.

[3] Fair value of $ 56 and $ 70 at September 30, 2016 and December 31, 2015 , respectively.