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Investment Securities - Summary of Unrealized Loss Positions on Investment Securities (Details) - USD ($) $ in Millions | Mar. 31, 2024 | Dec. 31, 2023
--- | --- | ---
Debt Securities, Available-for-sale [Line Items] |  |
Less than Twelve Months, Fair Value | $ 1,360 | $ 2,357
Less than Twelve Months, Unrealized Loss | 28 | 84
Twelve Months or Longer, Fair Value | 5,531 | 4,198
Twelve Months or Longer, Unrealized Loss | 899 | 777
Fair Value | 6,891 | 6,555
Unrealized Loss | 927 | 861
Other Debt Securities: | U. S. Treasury obligations |  |
Debt Securities, Available-for-sale [Line Items] |  |
Less than Twelve Months, Fair Value | 0 | 0
Less than Twelve Months, Unrealized Loss | 0 | 0
Twelve Months or Longer, Fair Value | 0 | 0
Twelve Months or Longer, Unrealized Loss | 0 | 0
Fair Value | 0 | 0
Unrealized Loss | 0 | 0
Other Debt Securities: | U.S. Government agency and GSE obligations |  |
Debt Securities, Available-for-sale [Line Items] |  |
Less than Twelve Months, Fair Value | 0 | 181
Less than Twelve Months, Unrealized Loss | 0 | 1
Twelve Months or Longer, Fair Value | 1,441 | 1,362
Twelve Months or Longer, Unrealized Loss | 311 | 290
Fair Value | 1,441 | 1,543
Unrealized Loss | 311 | 291
Other Debt Securities: | GSE certificates |  |
Debt Securities, Available-for-sale [Line Items] |  |
Less than Twelve Months, Fair Value | 53 | 312
Less than Twelve Months, Unrealized Loss | 1 | 5
Twelve Months or Longer, Fair Value | 1,087 | 843
Twelve Months or Longer, Unrealized Loss | 163 | 141
Fair Value | 1,140 | 1,155
Unrealized Loss | 164 | 146
Other Debt Securities: | Private Label CMOs |  |
Debt Securities, Available-for-sale [Line Items] |  |
Less than Twelve Months, Fair Value | 15 | 29
Less than Twelve Months, Unrealized Loss | 0 | 1
Twelve Months or Longer, Fair Value | 3 | 0
Twelve Months or Longer, Unrealized Loss | 0 | 0
Fair Value | 18 | 29
Unrealized Loss | 0 | 1
Other Debt Securities: | GSE CMOs |  |
Debt Securities, Available-for-sale [Line Items] |  |
Less than Twelve Months, Fair Value | 1,292 | 1,835
Less than Twelve Months, Unrealized Loss | 27 | 77
Twelve Months or Longer, Fair Value | 2,340 | 1,312
Twelve Months or Longer, Unrealized Loss | 385 | 304
Fair Value | 3,632 | 3,147
Unrealized Loss | 412 | 381
Other Debt Securities: | Asset-backed securities |  |
Debt Securities, Available-for-sale [Line Items] |  |
Less than Twelve Months, Fair Value | 0 | 0
Less than Twelve Months, Unrealized Loss | 0 | 0
Twelve Months or Longer, Fair Value | 207 | 228
Twelve Months or Longer, Unrealized Loss | 4 | 5
Fair Value | 207 | 228
Unrealized Loss | 4 | 5
Other Debt Securities: | Municipal bonds |  |
Debt Securities, Available-for-sale [Line Items] |  |
Less than Twelve Months, Fair Value | 0 | 0
Less than Twelve Months, Unrealized Loss | 0 | 0
Twelve Months or Longer, Fair Value | 6 | 6
Twelve Months or Longer, Unrealized Loss | 0 | 0
Fair Value | 6 | 6
Unrealized Loss | 0 | 0
Other Debt Securities: | Corporate bonds |  |
Debt Securities, Available-for-sale [Line Items] |  |
Less than Twelve Months, Fair Value | 0 | 0
Less than Twelve Months, Unrealized Loss | 0 | 0
Twelve Months or Longer, Fair Value | 341 | 343
Twelve Months or Longer, Unrealized Loss | 24 | 22
Fair Value | 341 | 343
Unrealized Loss | 24 | 22
Other Debt Securities: | Foreign notes |  |
Debt Securities, Available-for-sale [Line Items] |  |
Less than Twelve Months, Fair Value | 0 | 0
Less than Twelve Months, Unrealized Loss | 0 | 0
Twelve Months or Longer, Fair Value | 10 | 9
Twelve Months or Longer, Unrealized Loss | 0 | 1
Fair Value | 10 | 9
Unrealized Loss | 0 | 1
Other Debt Securities: | Capital trust notes |  |
Debt Securities, Available-for-sale [Line Items] |  |
Less than Twelve Months, Fair Value | 0 | 0
Less than Twelve Months, Unrealized Loss | 0 | 0
Twelve Months or Longer, Fair Value | 82 | 81
Twelve Months or Longer, Unrealized Loss | 10 | 12
Fair Value | 82 | 81
Unrealized Loss | 10 | 12
Equity securities: |  |
Debt Securities, Available-for-sale [Line Items] |  |
Less than Twelve Months, Fair Value | 0 | 0
Less than Twelve Months, Unrealized Loss | 0 | 0
Twelve Months or Longer, Fair Value | 14 | 14
Twelve Months or Longer, Unrealized Loss | 2 | 2
Fair Value | 14 | 14
Unrealized Loss | $ 2 | $ 2

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