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Investment Securities - Investment Available for Sale (Details) - USD ($) $ in Millions | Dec. 31, 2023 | Dec. 31, 2022
--- | --- | ---
Debt Securities, Available-for-sale [Line Items] |  |
Amortized Cost | $ 88,063 | $ 87,047
Allowance for Credit Losses | (4) | (3)
Gross Unrealized Gains | 214 | 154
Gross Unrealized Losses | (9,156) | (10,279)
Fair Value | 79,117 | 76,919
U.S. Treasury securities |  |
Debt Securities, Available-for-sale [Line Items] |  |
Amortized Cost | 5,330 | 5,129
Allowance for Credit Losses | 0 | 0
Gross Unrealized Gains | 1 | 2
Gross Unrealized Losses | (49) | (90)
Fair Value | 5,282 | 5,041
RMBS, Agency |  |
Debt Securities, Available-for-sale [Line Items] |  |
Amortized Cost | 71,294 | 71,212
Allowance for Credit Losses | 0 | 0
Gross Unrealized Gains | 104 | 53
Gross Unrealized Losses | (8,450) | (9,413)
Fair Value | 62,948 | 61,852
RMBS, Non-agency |  |
Debt Securities, Available-for-sale [Line Items] |  |
Amortized Cost | 610 | 653
Allowance for Credit Losses | (4) | (3)
Gross Unrealized Gains | 89 | 93
Gross Unrealized Losses | (5) | (6)
Fair Value | 690 | 737
Total RMBS |  |
Debt Securities, Available-for-sale [Line Items] |  |
Amortized Cost | 71,904 | 71,865
Allowance for Credit Losses | (4) | (3)
Gross Unrealized Gains | 193 | 146
Gross Unrealized Losses | (8,455) | (9,419)
Fair Value | 63,638 | 62,589
Agency CMBS |  |
Debt Securities, Available-for-sale [Line Items] |  |
Amortized Cost | 8,961 | 8,626
Allowance for Credit Losses | 0 | 0
Gross Unrealized Gains | 14 | 4
Gross Unrealized Losses | (652) | (760)
Fair Value | 8,323 | 7,870
Other securities |  |
Debt Securities, Available-for-sale [Line Items] |  |
Amortized Cost | 1,868 | 1,427
Allowance for Credit Losses | 0 | 0
Gross Unrealized Gains | 6 | 2
Gross Unrealized Losses | 0 | (10)
Fair Value | 1,874 | 1,419
Asset-backed Securities |  |
Debt Securities, Available-for-sale [Line Items] |  |
Fair Value | $ 1,400 | $ 707

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- Definition Amount, before tax, of unrealized gain in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale). + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 320 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 2 -Subparagraph (b) -Publisher FASB -URI https://asc.fasb.org//1943274/2147481800/320-10-50-2 + Details
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