Investment Securities (Maturities of Securities Available for Sale) (Details) - USD ($) $ in Millions	Dec. 31, 2021	Dec. 31, 2020
Available for sale securities, fair value
Within 1 year	$ 9,790
After 1 year through 5 years	48,023
After 5 years through 10 years	82,649
After 10 years	249,592
Fair Value	390,054	$ 337,400
Available for sale securities, amortized cost
Within 1 year	9,761
After 1 year through 5 years	47,336
After 5 years through 10 years	82,556
After 10 years	251,829
Amortized Cost	$ 391,482	330,248
Weighted-average yield
Within 1 year	1.28%
After 1 year through 5 years	1.89%
After 1 year through 5 years	1.78%
After 10 years	1.11%
Total	1.35%
U.S. agency mortgage-backed securities [Member]
Available for sale securities, fair value
Within 1 year	$ 3,483
After 1 year through 5 years	20,916
After 5 years through 10 years	71,705
After 10 years	238,251
Fair Value	334,355	290,353
Available for sale securities, amortized cost
Amortized Cost	335,803	283,911
U.S. Treasury securities [Member]
Available for sale securities, fair value
Within 1 year	4,049
After 1 year through 5 years	14,569
After 5 years through 10 years	2,664
After 10 years	0
Fair Value	21,282	10,656
Available for sale securities, amortized cost
Amortized Cost	21,394	10,631
Asset-backed securities [Member]
Available for sale securities, fair value
Within 1 year	0
After 1 year through 5 years	4,922
After 5 years through 10 years	3,003
After 10 years	9,621
Fair Value	17,546	18,898
Available for sale securities, amortized cost
Amortized Cost	17,547	18,808
Corporate debt securities [Member]
Available for sale securities, fair value
Within 1 year	1,634
After 1 year through 5 years	6,443
After 5 years through 10 years	4,267
After 10 years	0
Fair Value	12,344	12,796
Available for sale securities, amortized cost
Amortized Cost	12,310	12,408
U.S. state and municipal securities [Member]
Available for sale securities, fair value
Within 1 year	23
After 1 year through 5 years	150
After 5 years through 10 years	1,010
After 10 years	504
Fair Value	1,687	1,697
Available for sale securities, amortized cost
Amortized Cost	1,611	1,544
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	1,190
Fair Value	1,190	1,265
Available for sale securities, amortized cost
Amortized Cost	1,170	1,213
Certificates of deposit [Member]
Available for sale securities, fair value
Within 1 year	300
After 1 year through 5 years	699
After 5 years through 10 years	0
After 10 years	0
Fair Value	999	300
Available for sale securities, amortized cost
Amortized Cost	1,000	300
Foreign government agency securities [Member]
Available for sale securities, fair value
Within 1 year	101
After 1 year through 5 years	324
After 5 years through 10 years	0
After 10 years	0
Fair Value	425	1,413
Available for sale securities, amortized cost
Amortized Cost	425	1,411
Commercial paper [Member]
Available for sale securities, fair value
Within 1 year	200
After 1 year through 5 years	0
After 5 years through 10 years	0
After 10 years	0
Fair Value	200
Available for sale securities, amortized cost
Amortized Cost	200
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