Securities (Amortized Cost and Fair Value of Available-for-Sale and Held-to-Maturity Securities) (Detail) - USD ($) $ in Millions		Mar. 31, 2017	Dec. 31, 2016
Debt securities:
Less than 1 year	[1]	$ 187
1-5 years	[1]	6,316
5-10 years	[1]	21,358
Over 10 years	[1]	2,789
Equity securities		698
Available-for-sale and other securities, Amortized Cost		31,348	$ 31,024
Debt securities:
Less than 1 year	[1]	189
1-5 years	[1]	6,362
5-10 years	[1]	21,481
Over 10 years	[1]	2,800
Equity securities		699
Available-for-sale and other securities, fair value	[2]	31,531	31,183
Debt securities:
Less than 1 year	[1]	2
1-5 years	[1]	12
5-10 years	[1]	10
Over 10 years	[1]	2
Equity securities		0
Held-to-maturity securities, amortized cost	[3]	26	26
Debt securities:
Under 1 year	[1]	2
1-5 years	[1]	12
5-10 years	[1]	10
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 $ 31,348 and $ 31,024 at March 31, 2017 and December 31, 2016 , respectively.

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