Investment Securities - Investment Securities in an Unrealized Loss Position (Details) - USD ($) $ in Millions	Mar. 31, 2022	Dec. 31, 2021
AFS securities
AFS: Fair Value, Less than 12 Months	$ 61,118	$ 46,955
AFS: Fair Value, 12 Months or Longer	11,006	1,775
AFS: Fair Value, Total	72,124	48,730
AFS: Gross Unrealized Losses, Less than 12 Months	2,292	607
AFS: Gross Unrealized Losses, 12 Months or Longer	610	32
AFS: Gross Unrealized Losses, Total	2,902	639
U.S. Treasury securities
AFS securities
AFS: Fair Value, Less than 12 Months	39,314	31,459
AFS: Fair Value, 12 Months or Longer	6,828	0
AFS: Fair Value, Total	46,142	31,459
AFS: Gross Unrealized Losses, Less than 12 Months	1,252	296
AFS: Gross Unrealized Losses, 12 Months or Longer	267	0
AFS: Gross Unrealized Losses, Total	1,519	296
U.S. agency securities
AFS securities
AFS: Fair Value, Less than 12 Months	16,478	12,283
AFS: Fair Value, 12 Months or Longer	3,624	1,167
AFS: Fair Value, Total	20,102	13,450
AFS: Gross Unrealized Losses, Less than 12 Months	816	219
AFS: Gross Unrealized Losses, 12 Months or Longer	327	22
AFS: Gross Unrealized Losses, Total	1,143	241
Agency CMBS
AFS securities
AFS: Fair Value, Less than 12 Months	3,634	2,872
AFS: Fair Value, 12 Months or Longer	142	10
AFS: Fair Value, Total	3,776	2,882
AFS: Gross Unrealized Losses, Less than 12 Months	182	89
AFS: Gross Unrealized Losses, 12 Months or Longer	7	0
AFS: Gross Unrealized Losses, Total	189	89
State and municipal securities
AFS securities
AFS: Fair Value, Less than 12 Months	1,112	21
AFS: Fair Value, Total	1,112	21
AFS: Gross Unrealized Losses, Less than 12 Months	37	2
AFS: Gross Unrealized Losses, Total	37	2
FFELP student loan ABS:
AFS securities
AFS: Fair Value, Less than 12 Months	580	320
AFS: Fair Value, 12 Months or Longer	412	591
AFS: Fair Value, Total	992	911
AFS: Gross Unrealized Losses, Less than 12 Months	5	1
AFS: Gross Unrealized Losses, 12 Months or Longer	9	10
AFS: Gross Unrealized Losses, Total	$ 14	$ 11

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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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