Securities (Amortized Cost and Fair Value of Available-for-Sale and Held-to-Maturity Securities) (Detail) - USD ($) $ in Millions		Mar. 31, 2019	Dec. 31, 2018
Debt securities:
Less than 1 year	[1]	$ 821
1-5 years	[1]	11,521
5-10 years	[1]	17,148
Over 10 years	[1]	4,713
Other securities		581
Available-for-sale debt securities, amortized cost		34,784	$ 33,128
Debt securities:
Less than 1 year	[1]	819
1-5 years	[1]	11,655
5-10 years	[1]	17,253
Over 10 years	[1]	4,740
Other securities		581
Available-for-sale debt and other securities, fair value	[2]	35,048	32,830
Debt securities:
Less than 1 year	[1]	0
1-5 years	[1]	16
5-10 years	[1]	0
Over 10 years	[1]	5
Other securities		0
Held-to-maturity securities, amortized cost	[3]	21	18
Debt securities:
Under 1 year	[1]	0
1-5 years	[1]	16
5-10 years	[1]	0
Over 10 years	[1]	5
Other securities		0
Held-to-maturity securities, fair value		$ 21	$ 18

[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 $ 34,784 and $ 33,128 at March 31, 2019 and December 31, 2018 , respectively.

[3] Fair value of $ 21 and $ 18 at March 31, 2019 and December 31, 2018 , respectively.