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Investment Securities - Summary of Investment Securities (Details) - USD ($) $ in Millions | Sep. 30, 2025 | Dec. 31, 2024
--- | --- | ---
Debt securities available for sale |  |
Amortized Cost | $ 15,696 | $ 11,295
Gross Unrealized Gain | 88 | 39
Gross Unrealized Loss | 732 | 932
Fair Value | 15,052 | 10,402
Amortized cost of investment securities | 2 | 3
Interest receivable | $ 43 | $ 35
Debt Securities, Available-for-Sale, Accrued Interest, after Allowance for Credit Loss, Statement of Financial Position [Extensible Enumeration] | Other assets | Other assets
Asset Pledged as Collateral |  |
Debt securities available for sale |  |
Fair value | $ 14,800 | $ 10,200
Mortgage-Related Debt Securities: |  |
Debt securities available for sale |  |
Amortized Cost | 12,756 | 9,155
Gross Unrealized Gain | 68 | 33
Gross Unrealized Loss | 497 | 615
Fair Value | 12,327 | 8,573
GSE CMOs |  |
Debt securities available for sale |  |
Amortized Cost | 11,476 | 7,724
Gross Unrealized Gain | 56 | 27
Gross Unrealized Loss | 371 | 447
Fair Value | 11,161 | 7,304
GSE certificates |  |
Debt securities available for sale |  |
Amortized Cost | 1,130 | 1,273
Gross Unrealized Gain | 1 | 0
Gross Unrealized Loss | 126 | 167
Fair Value | 1,005 | 1,106
Private label CMOs |  |
Debt securities available for sale |  |
Amortized Cost | 150 | 158
Gross Unrealized Gain | 11 | 6
Gross Unrealized Loss | 0 | 1
Fair Value | 161 | 163
Other Debt Securities: |  |
Debt securities available for sale |  |
Amortized Cost | 2,940 | 2,140
Gross Unrealized Gain | 20 | 6
Gross Unrealized Loss | 235 | 317
Fair Value | 2,725 | 1,829
GSE debentures |  |
Debt securities available for sale |  |
Amortized Cost | 1,502 | 1,502
Gross Unrealized Gain | 0 | 0
Gross Unrealized Loss | 216 | 299
Fair Value | 1,286 | 1,203
U. S. treasury obligations |  |
Debt securities available for sale |  |
Amortized Cost | 1,000 |
Gross Unrealized Gain | 14 |
Gross Unrealized Loss | 0 |
Fair Value | 1,014 |
Asset-backed securities |  |
Debt securities available for sale |  |
Amortized Cost | 222 | 237
Gross Unrealized Gain | 0 | 1
Gross Unrealized Loss | 4 | 2
Fair Value | 218 | 236
Corporate bonds |  |
Debt securities available for sale |  |
Amortized Cost | 164 | 314
Gross Unrealized Gain | 0 | 0
Gross Unrealized Loss | 7 | 6
Fair Value | 157 | 308
Capital trust notes |  |
Debt securities available for sale |  |
Amortized Cost | 47 | 47
Gross Unrealized Gain | 6 | 5
Gross Unrealized Loss | 8 | 10
Fair Value | 45 | 42
Foreign notes |  |
Debt securities available for sale |  |
Amortized Cost |  | 35
Gross Unrealized Gain |  | 0
Gross Unrealized Loss |  | 0
Fair Value |  | 35
Municipal bonds |  |
Debt securities available for sale |  |
Amortized Cost | 5 | 5
Gross Unrealized Gain | 0 | 0
Gross Unrealized Loss | 0 | 0
Fair Value | $ 5 | $ 5

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