Investment Securities - Summary of Unrealized Loss Positions on Investment Securities (Details) - USD ($) $ in Millions	Sep. 30, 2023	Dec. 31, 2022
Debt Securities, Available-for-sale [Line Items]
Less than Twelve Months, Fair Value	$ 3,955	$ 5,658
Less than Twelve Months, Unrealized Loss	208	122
Twelve Months or Longer, Fair Value	4,101	2,911
Twelve Months or Longer, Unrealized Loss	982	751
Fair Value	8,056	8,569
Unrealized Loss	1,190	873
Debt Securities \| U. S. Treasury obligations
Debt Securities, Available-for-sale [Line Items]
Less than Twelve Months, Fair Value	0	1,487
Less than Twelve Months, Unrealized Loss	0	4
Twelve Months or Longer, Fair Value	0	0
Twelve Months or Longer, Unrealized Loss	0	0
Fair Value	0	1,487
Unrealized Loss	0	4
Debt Securities \| U.S. Government agency and GSE obligations
Debt Securities, Available-for-sale [Line Items]
Less than Twelve Months, Fair Value	216	243
Less than Twelve Months, Unrealized Loss	1	5
Twelve Months or Longer, Fair Value	1,367	1,156
Twelve Months or Longer, Unrealized Loss	382	346
Fair Value	1,583	1,399
Unrealized Loss	383	351
Debt Securities \| GSE certificates
Debt Securities, Available-for-sale [Line Items]
Less than Twelve Months, Fair Value	341	871
Less than Twelve Months, Unrealized Loss	23	46
Twelve Months or Longer, Fair Value	823	420
Twelve Months or Longer, Unrealized Loss	191	114
Fair Value	1,164	1,291
Unrealized Loss	214	160
Debt Securities \| Private Label CMOs
Debt Securities, Available-for-sale [Line Items]
Less than Twelve Months, Fair Value	140
Less than Twelve Months, Unrealized Loss	3
Twelve Months or Longer, Fair Value	0
Twelve Months or Longer, Unrealized Loss	0
Fair Value	140
Unrealized Loss	3
Debt Securities \| GSE CMOs
Debt Securities, Available-for-sale [Line Items]
Less than Twelve Months, Fair Value	3,234	2,219
Less than Twelve Months, Unrealized Loss	180	36
Twelve Months or Longer, Fair Value	1,117	925
Twelve Months or Longer, Unrealized Loss	352	264
Fair Value	4,351	3,144
Unrealized Loss	532	300
Debt Securities \| Asset-backed securities
Debt Securities, Available-for-sale [Line Items]
Less than Twelve Months, Fair Value	0	61
Less than Twelve Months, Unrealized Loss	0	2
Twelve Months or Longer, Fair Value	280	262
Twelve Months or Longer, Unrealized Loss	6	12
Fair Value	280	323
Unrealized Loss	6	14
Debt Securities \| Municipal bonds
Debt Securities, Available-for-sale [Line Items]
Less than Twelve Months, Fair Value	0	9
Less than Twelve Months, Unrealized Loss	0	0
Twelve Months or Longer, Fair Value	6	7
Twelve Months or Longer, Unrealized Loss	1	0
Fair Value	6	16
Unrealized Loss	1	0
Debt Securities \| Corporate bonds
Debt Securities, Available-for-sale [Line Items]
Less than Twelve Months, Fair Value	0	698
Less than Twelve Months, Unrealized Loss	0	27
Twelve Months or Longer, Fair Value	405	97
Twelve Months or Longer, Unrealized Loss	35	3
Fair Value	405	795
Unrealized Loss	35	30
Debt Securities \| Foreign notes
Debt Securities, Available-for-sale [Line Items]
Less than Twelve Months, Fair Value	24	20
Less than Twelve Months, Unrealized Loss	1	0
Twelve Months or Longer, Fair Value	9	0
Twelve Months or Longer, Unrealized Loss	1	0
Fair Value	33	20
Unrealized Loss	2	0
Debt Securities \| Capital trust notes
Debt Securities, Available-for-sale [Line Items]
Less than Twelve Months, Fair Value	0	46
Less than Twelve Months, Unrealized Loss	0	2
Twelve Months or Longer, Fair Value	81	34
Twelve Months or Longer, Unrealized Loss	11	10
Fair Value	81	80
Unrealized Loss	11	12
Equity Securities
Debt Securities, Available-for-sale [Line Items]
Less than Twelve Months, Fair Value	0	4
Less than Twelve Months, Unrealized Loss	0	0
Twelve Months or Longer, Fair Value	13	10
Twelve Months or Longer, Unrealized Loss	3	2
Fair Value	13	14
Unrealized Loss	$ 3	$ 2

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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