Investment Securities (Available For Sale with Unrealized Losses, Aggregated by Category and Period of Continuous Unrealized Loss) (Details) - USD ($) $ in Millions	Sep. 30, 2021	Dec. 31, 2020
Available for sale securities:
Less than 12 months Fair Value	$ 181,738	$ 63,104
Less than 12 months Unrealized Losses	2,581	564
12 months or longer Fair Value	21,252	10,596
12 months or longer Unrealized Losses	467	83
Total Fair Value	202,990	73,700
Total Unrealized Losses	3,048	647
U.S. agency mortgage-backed securities [Member]
Available for sale securities:
Less than 12 months Fair Value	165,770	61,706
Less than 12 months Unrealized Losses	2,426	551
12 months or longer Fair Value	18,326	4,774
12 months or longer Unrealized Losses	441	12
Total Fair Value	184,096	66,480
Total Unrealized Losses	2,867	563
Corporate debt securities [Member]
Available for sale securities:
Less than 12 months Fair Value	3,462
Less than 12 months Unrealized Losses	76
12 months or longer Fair Value	52
12 months or longer Unrealized Losses	3
Total Fair Value	3,514
Total Unrealized Losses	79
Asset-backed securities [Member]
Available for sale securities:
Less than 12 months Fair Value	2,893	1,398
Less than 12 months Unrealized Losses	21	13
12 months or longer Fair Value	2,848	5,822
12 months or longer Unrealized Losses	23	71
Total Fair Value	5,741	7,220
Total Unrealized Losses	44	$ 84
U.S. Treasury securities [Member]
Available for sale securities:
Less than 12 months Fair Value	9,018
Less than 12 months Unrealized Losses	55
12 months or longer Fair Value	21
12 months or longer Unrealized Losses	0
Total Fair Value	9,039
Total Unrealized Losses	55
U.S. state and municipal securities [Member]
Available for sale securities:
Less than 12 months Fair Value	96
Less than 12 months Unrealized Losses	2
12 months or longer Fair Value	5
12 months or longer Unrealized Losses	0
Total Fair Value	101
Total Unrealized Losses	2
Certificates of deposit [Member]
Available for sale securities:
Less than 12 months Fair Value	499
Less than 12 months Unrealized Losses	1
12 months or longer Fair Value	0
12 months or longer Unrealized Losses	0
Total Fair Value	499
Total Unrealized Losses	$ 1

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Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), in continuous unrealized loss position for more than 12 months, without allowance for credit loss. Includes beneficial interest in securitized financial asset.

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Amount of accumulated unrealized loss on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), in continuous unrealized loss position for 12 months or longer, without allowance for credit loss. Includes beneficial interest in securitized financial asset.

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Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), in continuous unrealized loss position for less than 12 months, without allowance for credit loss. Includes beneficial interest in securitized financial asset.

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