Investment Securities (Maturities of Securities Available for Sale) (Details) - USD ($) $ in Millions	Jun. 30, 2021	Dec. 31, 2020
Available for sale securities, fair value
Within 1 year	$ 13,072
After 1 year through 5 years	35,146
After 5 years through 10 years	74,499
After 10 years	236,905
Fair Value	359,622	$ 337,400
Available for sale securities, amortized cost
Within 1 year	13,034
After 1 year through 5 years	34,010
After 5 years through 10 years	73,019
After 10 years	236,376
Amortized Cost	356,439	330,248
U.S. agency mortgage-backed securities [Member]
Available for sale securities, fair value
Within 1 year	2,790
After 1 year through 5 years	20,758
After 5 years through 10 years	65,817
After 10 years	225,403
Fair Value	314,768	290,353
Available for sale securities, amortized cost
Amortized Cost	312,045	283,911
Asset-backed securities [Member]
Available for sale securities, fair value
Within 1 year	31
After 1 year through 5 years	5,794
After 5 years through 10 years	2,112
After 10 years	9,591
Fair Value	17,528	18,898
Available for sale securities, amortized cost
Amortized Cost	17,436	18,808
Corporate debt securities [Member]
Available for sale securities, fair value
Within 1 year	2,986
After 1 year through 5 years	6,240
After 5 years through 10 years	3,867
After 10 years	0
Fair Value	13,093	12,796
Available for sale securities, amortized cost
Amortized Cost	12,882	12,408
U.S. Treasury securities [Member]
Available for sale securities, fair value
Within 1 year	6,489
After 1 year through 5 years	594
After 5 years through 10 years	1,746
After 10 years	0
Fair Value	8,829	10,656
Available for sale securities, amortized cost
Amortized Cost	8,814	10,631
U.S. state and municipal securities [Member]
Available for sale securities, fair value
Within 1 year	23
After 1 year through 5 years	105
After 5 years through 10 years	957
After 10 years	637
Fair Value	1,722	1,697
Available for sale securities, amortized cost
Amortized Cost	1,623	1,544
Foreign government agency securities [Member]
Available for sale securities, fair value
Within 1 year	553
After 1 year through 5 years	855
After 5 years through 10 years	0
After 10 years	0
Fair Value	1,408	1,413
Available for sale securities, amortized cost
Amortized Cost	1,408	1,411
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	1,248
Fair Value	1,248	1,265
Available for sale securities, amortized cost
Amortized Cost	1,209	1,213
Certificates of deposit [Member]
Available for sale securities, fair value
Within 1 year	200
After 1 year through 5 years	800
After 5 years through 10 years	0
After 10 years	0
Fair Value	1,000	300
Available for sale securities, amortized cost
Amortized Cost	1,000	300
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	26
Fair Value	26	22
Available for sale securities, amortized cost
Amortized Cost	$ 22	$ 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), with single maturity date and allocated without single maturity date, maturing in sixth through tenth fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

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