Securities (Amortized Cost and Fair Value of Available-for-Sale and Held-to-Maturity Securities) (Detail) - USD ($) $ in Millions		Jun. 30, 2017	Dec. 31, 2016
Debt securities:
Less than 1 year	[1]	$ 144
1-5 years	[1]	7,205
5-10 years	[1]	20,787
Over 10 years	[1]	2,657
Equity securities		699
Available-for-sale and other securities, Amortized Cost		31,492	$ 31,024
Debt securities:
Less than 1 year	[1]	146
1-5 years	[1]	7,276
5-10 years	[1]	21,023
Over 10 years	[1]	2,678
Equity securities		700
Available-for-sale and other securities, fair value	[2]	31,823	31,183
Debt securities:
Less than 1 year	[1]	6
1-5 years	[1]	9
5-10 years	[1]	9
Over 10 years	[1]	2
Equity securities		0
Held-to-maturity securities, amortized cost	[3]	26	26
Debt securities:
Under 1 year	[1]	6
1-5 years	[1]	9
5-10 years	[1]	9
Over 10 years	[1]	2
Equity securities		0
Held-to-maturity securities, fair value		$ 26	$ 26

[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 $ 31,492 and $ 31,024 at June 30, 2017 and December 31, 2016 , respectively.

[3] Fair value of $ 26 and $ 26 at June 30, 2017 and December 31, 2016 , respectively.