Investment Securities (Maturities of Securities Available for Sale and Held to Maturity) (Details) - USD ($) $ in Millions	Sep. 30, 2020	Dec. 31, 2019
Available for sale securities, fair value
Within 1 year	$ 13,894
After 1 year through 5 years	36,929
After 5 years through 10 years	68,171
After 10 years	184,764
Fair Value	303,758	$ 61,422
Available for sale securities, amortized cost
Within 1 year	13,820
After 1 year through 5 years	35,591
After 5 years through 10 years	65,043
After 10 years	181,745
Amortized Cost	296,199	61,155
U.S. agency mortgage-backed securities [Member]
Available for sale securities, fair value
Within 1 year	1,437
After 1 year through 5 years	21,995
After 5 years through 10 years	60,619
After 10 years	174,215
Fair Value	258,266	46,155
Available for sale securities, amortized cost
Amortized Cost	251,323	45,964
Asset-backed securities [Member]
Available for sale securities, fair value
Within 1 year	10
After 1 year through 5 years	6,402
After 5 years through 10 years	4,469
After 10 years	8,440
Fair Value	19,321	4,987
Available for sale securities, amortized cost
Amortized Cost	19,320	4,970
Corporate debt securities [Member]
Available for sale securities, fair value
Within 1 year	4,262
After 1 year through 5 years	7,000
After 5 years through 10 years	2,318
After 10 years	0
Fair Value	13,580	5,484
Available for sale securities, amortized cost
Amortized Cost	13,192	5,427
U.S. Treasury securities [Member]
Available for sale securities, fair value
Within 1 year	7,559
After 1 year through 5 years	343
After 5 years through 10 years	0
After 10 years	0
Fair Value	7,902	3,384
Available for sale securities, amortized cost
Amortized Cost	7,871	3,387
U.S. state and municipal securities [Member]
Available for sale securities, fair value
Within 1 year	0
After 1 year through 5 years	104
After 5 years through 10 years	765
After 10 years	821
Fair Value	1,690
Available for sale securities, amortized cost
Amortized Cost	1,548
Non-agency commercial mortgage-backed securities [Member]
Available for sale securities, fair value
Within 1 year	0
After 1 year through 5 years	0
After 5 years through 10 years	0
After 10 years	1,266
Fair Value	1,266	13
Available for sale securities, amortized cost
Amortized Cost	1,214	13
Certificates of deposit [Member]
Available for sale securities, fair value
Within 1 year	501
After 1 year through 5 years	0
After 5 years through 10 years	0
After 10 years	0
Fair Value	501	1,004
Available for sale securities, amortized cost
Amortized Cost	500	$ 1,000
Foreign government agency securities [Member]
Available for sale securities, fair value
Within 1 year	125
After 1 year through 5 years	1,085
After 5 years through 10 years	0
After 10 years	0
Fair Value	1,210
Available for sale securities, amortized cost
Amortized Cost	1,209
Other [Member]
Available for sale securities, fair value
Within 1 year	0
After 1 year through 5 years	0
After 5 years through 10 years	0
After 10 years	22
Fair Value	22
Available for sale securities, amortized cost
Amortized Cost	$ 22

Amortized cost of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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