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Fair Value Measurement - Quantitative Information about Level 3 Fair Value Measurements (Details) $ in Millions | Sep. 30, 2025 USD ($) | Dec. 31, 2024 USD ($)
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Fair Value Measurement Inputs and Valuation Techniques [Line Items] |  |
Fair Value | $ 89,733 | $ 83,013
Recurring |  |
Fair Value Measurement Inputs and Valuation Techniques [Line Items] |  |
Fair Value | 89,733 | 83,013
Recurring | Level 3 |  |
Fair Value Measurement Inputs and Valuation Techniques [Line Items] |  |
Fair Value | 126 | 118
Retained interests in securitizations | 29 | 34
Net derivative assets (liabilities) | 108 | 69
Total RMBS |  |
Fair Value Measurement Inputs and Valuation Techniques [Line Items] |  |
Fair Value | 68,899 | 65,328
Total RMBS | Recurring |  |
Fair Value Measurement Inputs and Valuation Techniques [Line Items] |  |
Fair Value | 68,899 | 65,328
Total RMBS | Recurring | Level 3 |  |
Fair Value Measurement Inputs and Valuation Techniques [Line Items] |  |
Fair Value | 126 | 116
CMBS | Recurring |  |
Fair Value Measurement Inputs and Valuation Techniques [Line Items] |  |
Fair Value | 8,440 | 7,825
CMBS | Recurring | Level 3 |  |
Fair Value Measurement Inputs and Valuation Techniques [Line Items] |  |
Fair Value | $ 0 | $ 2
Yield | Total RMBS | Recurring | Level 3 | Discounted cash flows | Minimum |  |
Fair Value Measurement Inputs and Valuation Techniques [Line Items] |  |
Securities available-for-sale, measurement input | 0.05 | 0.06
Yield | Total RMBS | Recurring | Level 3 | Discounted cash flows | Maximum |  |
Fair Value Measurement Inputs and Valuation Techniques [Line Items] |  |
Securities available-for-sale, measurement input | 0.10 | 0.10
Yield | Total RMBS | Recurring | Level 3 | Discounted cash flows | Weighted average |  |
Fair Value Measurement Inputs and Valuation Techniques [Line Items] |  |
Securities available-for-sale, measurement input | 0.06 | 0.06
Yield | CMBS | Recurring | Level 3 | Discounted cash flows | Minimum |  |
Fair Value Measurement Inputs and Valuation Techniques [Line Items] |  |
Securities available-for-sale, measurement input | 0.04 | 0.05
Yield | CMBS | Recurring | Level 3 | Discounted cash flows | Maximum |  |
Fair Value Measurement Inputs and Valuation Techniques [Line Items] |  |
Securities available-for-sale, measurement input | 0.04 | 0.07
Yield | CMBS | Recurring | Level 3 | Discounted cash flows | Weighted average |  |
Fair Value Measurement Inputs and Valuation Techniques [Line Items] |  |
Securities available-for-sale, measurement input | 0.04 | 0.07
Life of receivables (months) | Recurring | Level 3 | Discounted cash flows | Minimum |  |
Fair Value Measurement Inputs and Valuation Techniques [Line Items] |  |
Retained interests, measurement input, life of receivables | 34 months | 31 months
Life of receivables (months) | Recurring | Level 3 | Discounted cash flows | Maximum |  |
Fair Value Measurement Inputs and Valuation Techniques [Line Items] |  |
Retained interests, measurement input, life of receivables | 68 months | 81 months
Voluntary prepayment rate | Recurring | Level 3 | Discounted cash flows | Minimum |  |
Fair Value Measurement Inputs and Valuation Techniques [Line Items] |  |
Retained interests, measurement input | 0.08 | 0.07
Voluntary prepayment rate | Recurring | Level 3 | Discounted cash flows | Maximum |  |
Fair Value Measurement Inputs and Valuation Techniques [Line Items] |  |
Retained interests, measurement input | 0.08 | 0.09
Voluntary prepayment rate | Total RMBS | Recurring | Level 3 | Discounted cash flows | Minimum |  |
Fair Value Measurement Inputs and Valuation Techniques [Line Items] |  |
Securities available-for-sale, measurement input | 0 | 0
Voluntary prepayment rate | Total RMBS | Recurring | Level 3 | Discounted cash flows | Maximum |  |
Fair Value Measurement Inputs and Valuation Techniques [Line Items] |  |
Securities available-for-sale, measurement input | 0.16 | 0.12
Voluntary prepayment rate | Total RMBS | Recurring | Level 3 | Discounted cash flows | Weighted average |  |
Fair Value Measurement Inputs and Valuation Techniques [Line Items] |  |
Securities available-for-sale, measurement input | 0.07 | 0.07
Discount rate | Recurring | Level 3 | Discounted cash flows | Minimum |  |
Fair Value Measurement Inputs and Valuation Techniques [Line Items] |  |
Retained interests, measurement input | 0.05 | 0.05
Discount rate | Recurring | Level 3 | Discounted cash flows | Maximum |  |
Fair Value Measurement Inputs and Valuation Techniques [Line Items] |  |
Retained interests, measurement input | 0.13 | 0.15
Default rate | Recurring | Level 3 | Discounted cash flows | Minimum |  |
Fair Value Measurement Inputs and Valuation Techniques [Line Items] |  |
Retained interests, measurement input | 0.01 | 0.01
Default rate | Recurring | Level 3 | Discounted cash flows | Maximum |  |
Fair Value Measurement Inputs and Valuation Techniques [Line Items] |  |
Retained interests, measurement input | 0.01 | 0.01
Default rate | Total RMBS | Recurring | Level 3 | Discounted cash flows | Minimum |  |
Fair Value Measurement Inputs and Valuation Techniques [Line Items] |  |
Securities available-for-sale, measurement input | 0 | 0
Default rate | Total RMBS | Recurring | Level 3 | Discounted cash flows | Maximum |  |
Fair Value Measurement Inputs and Valuation Techniques [Line Items] |  |
Securities available-for-sale, measurement input | 0.06 | 0.06
Default rate | Total RMBS | Recurring | Level 3 | Discounted cash flows | Weighted average |  |
Fair Value Measurement Inputs and Valuation Techniques [Line Items] |  |
Securities available-for-sale, measurement input | 0.01 | 0.01
Loss severity | Recurring | Level 3 | Discounted cash flows | Minimum |  |
Fair Value Measurement Inputs and Valuation Techniques [Line Items] |  |
Retained interests, measurement input | 0.49 | 0.44
Loss severity | Recurring | Level 3 | Discounted cash flows | Maximum |  |
Fair Value Measurement Inputs and Valuation Techniques [Line Items] |  |
Retained interests, measurement input | 0.49 | 1.55
Loss severity | Total RMBS | Recurring | Level 3 | Discounted cash flows | Minimum |  |
Fair Value Measurement Inputs and Valuation Techniques [Line Items] |  |
Securities available-for-sale, measurement input | 0.25 | 0.25
Loss severity | Total RMBS | Recurring | Level 3 | Discounted cash flows | Maximum |  |
Fair Value Measurement Inputs and Valuation Techniques [Line Items] |  |
Securities available-for-sale, measurement input | 0.75 | 0.80
Loss severity | Total RMBS | Recurring | Level 3 | Discounted cash flows | Weighted average |  |
Fair Value Measurement Inputs and Valuation Techniques [Line Items] |  |
Securities available-for-sale, measurement input | 0.56 | 0.61
Swap rates | Recurring | Level 3 | Discounted cash flows | Minimum |  |
Fair Value Measurement Inputs and Valuation Techniques [Line Items] |  |
Net derivative assets (liabilities), measurement input | 0.03 | 0.04
Swap rates | Recurring | Level 3 | Discounted cash flows | Maximum |  |
Fair Value Measurement Inputs and Valuation Techniques [Line Items] |  |
Net derivative assets (liabilities), measurement input | 0.04 | 0.04
Swap rates | Recurring | Level 3 | Discounted cash flows | Weighted average |  |
Fair Value Measurement Inputs and Valuation Techniques [Line Items] |  |
Net derivative assets (liabilities), measurement input | 0.03 | 0.04

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