Investment Securities (Available For Sale with Unrealized Losses, Aggregated by Category and Period of Continuous Unrealized Loss) (Details) - USD ($) $ in Millions	Jun. 30, 2021	Dec. 31, 2020
Available for sale securities:
Less than 12 months Fair Value	$ 157,782	$ 63,104
Less than 12 months Unrealized Losses	2,203	564
12 months or longer Fair Value	9,165	10,596
12 months or longer Unrealized Losses	45	83
Total Fair Value	166,947	73,700
Total Unrealized Losses	2,248	647
U.S. agency mortgage-backed securities [Member]
Available for sale securities:
Less than 12 months Fair Value	148,997	61,706
Less than 12 months Unrealized Losses	2,122	551
12 months or longer Fair Value	5,304	4,774
12 months or longer Unrealized Losses	17	12
Total Fair Value	154,301	66,480
Total Unrealized Losses	2,139	563
Corporate debt securities [Member]
Available for sale securities:
Less than 12 months Fair Value	2,227
Less than 12 months Unrealized Losses	57
12 months or longer Fair Value	0
12 months or longer Unrealized Losses	0
Total Fair Value	2,227
Total Unrealized Losses	57
Asset-backed securities [Member]
Available for sale securities:
Less than 12 months Fair Value	1,916	1,398
Less than 12 months Unrealized Losses	16	13
12 months or longer Fair Value	3,861	5,822
12 months or longer Unrealized Losses	28	71
Total Fair Value	5,777	7,220
Total Unrealized Losses	44	$ 84
U.S. Treasury securities [Member]
Available for sale securities:
Less than 12 months Fair Value	3,872
Less than 12 months Unrealized Losses	6
12 months or longer Fair Value	0
12 months or longer Unrealized Losses	0
Total Fair Value	3,872
Total Unrealized Losses	6
U.S. state and municipal securities [Member]
Available for sale securities:
Less than 12 months Fair Value	65
Less than 12 months Unrealized Losses	1
12 months or longer Fair Value	0
12 months or longer Unrealized Losses	0
Total Fair Value	65
Total Unrealized Losses	1
Foreign government agency securities [Member]
Available for sale securities:
Less than 12 months Fair Value	705
Less than 12 months Unrealized Losses	1
12 months or longer Fair Value	0
12 months or longer Unrealized Losses	0
Total Fair Value	705
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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