Investment Securities (Maturities of Securities Available for Sale and Held to Maturity) (Details) - USD ($) $ in Millions	Mar. 31, 2020	Dec. 31, 2019
Available for sale securities, fair value
Within 1 year	$ 7,543
After 1 year through 5 years	35,590
After 5 years through 10 years	59,581
After 10 years	118,518
Fair Value	221,232	$ 61,422
Available for sale securities, amortized cost
Within 1 year	7,531
After 1 year through 5 years	35,024
After 5 years through 10 years	57,258
After 10 years	116,060
Amortized Cost	215,873	61,155
U.S. agency mortgage-backed securities [Member]
Available for sale securities, fair value
Within 1 year	1,158
After 1 year through 5 years	18,885
After 5 years through 10 years	51,687
After 10 years	107,865
Fair Value	179,595	46,155
Available for sale securities, amortized cost
Amortized Cost	173,812	45,964
Asset-backed securities [Member]
Available for sale securities, fair value
Within 1 year	43
After 1 year through 5 years	7,818
After 5 years through 10 years	6,091
After 10 years	8,529
Fair Value	22,481	4,987
Available for sale securities, amortized cost
Amortized Cost	23,077	4,970
Corporate debt securities [Member]
Available for sale securities, fair value
Within 1 year	2,410
After 1 year through 5 years	7,612
After 5 years through 10 years	1,200
After 10 years	0
Fair Value	11,222	5,484
Available for sale securities, amortized cost
Amortized Cost	11,192	5,427
U.S. Treasury securities [Member]
Available for sale securities, fair value
Within 1 year	2,834
After 1 year through 5 years	830
After 5 years through 10 years	0
After 10 years	0
Fair Value	3,664	3,384
Available for sale securities, amortized cost
Amortized Cost	3,616	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	98
After 5 years through 10 years	603
After 10 years	877
Fair Value	1,578
Available for sale securities, amortized cost
Amortized Cost	1,493
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	1,226
Fair Value	1,226	13
Available for sale securities, amortized cost
Amortized Cost	1,215	13
Certificates of deposit [Member]
Available for sale securities, fair value
Within 1 year	702
After 1 year through 5 years	296
After 5 years through 10 years	0
After 10 years	0
Fair Value	998	1,004
Available for sale securities, amortized cost
Amortized Cost	1,000	1,000
Commercial paper [Member]
Available for sale securities, fair value
Within 1 year	396
After 1 year through 5 years	0
After 5 years through 10 years	0
After 10 years	0
Fair Value	396	395
Available for sale securities, amortized cost
Amortized Cost	397	$ 394
Foreign government agency securities [Member]
Available for sale securities, fair value
Within 1 year	0
After 1 year through 5 years	51
After 5 years through 10 years	0
After 10 years	0
Fair Value	51
Available for sale securities, amortized cost
Amortized Cost	50
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	21
Fair Value	21
Available for sale securities, amortized cost
Amortized Cost	$ 21

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

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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