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Fair Value of Financial Instruments - Additional Information (Details) | 3 Months Ended | 9 Months Ended
--- | --- | ---
Sep. 30, 2019 USD ($) | Sep. 30, 2019 USD ($)
Residential loans |  |
Fair Value Measurement Inputs and Valuation Techniques [Line Items] |  |
Fair value option elected aggregate carrying amount, asset | $ 2,670,000,000 | $ 5,200,000,000
Business purpose residential loans, at fair value |  |
Fair Value Measurement Inputs and Valuation Techniques [Line Items] |  |
Fair value option elected aggregate carrying amount, asset | 124,000,000 | 301,000,000
Multifamily loans |  |
Fair Value Measurement Inputs and Valuation Techniques [Line Items] |  |
Fair value option elected aggregate carrying amount, asset | $ 0 | $ 1,430,000,000
Real estate securities | Maximum |  |
Fair Value Measurement Inputs and Valuation Techniques [Line Items] |  |
Dealer marks of securities (as a percent) | 83.00% | 83.00%
Carrying value for which dealer quotes have been received (as a percent) | 95.00% | 95.00%
Difference of internal valuation than dealer marks (as a percent) | 1.00% | 1.00%
Home appreciation options |  |
Fair Value Measurement Inputs and Valuation Techniques [Line Items] |  |
Fair value option elected aggregate carrying amount, asset | $ 11,000,000 |
Excess MSR |  |
Fair Value Measurement Inputs and Valuation Techniques [Line Items] |  |
Fair value option elected aggregate carrying amount, asset | 1,000,000 | $ 8,000,000
Servicer advance investments |  |
Fair Value Measurement Inputs and Valuation Techniques [Line Items] |  |
Fair value option elected aggregate carrying amount, asset | 1,000,000 | 70,000,000
Residential Subordinate Securities | Subordinate Securities |  |
Fair Value Measurement Inputs and Valuation Techniques [Line Items] |  |
Fair value option elected aggregate carrying amount, asset | 40,000,000 | 247,000,000
Residential Senior Securities |  |
Fair Value Measurement Inputs and Valuation Techniques [Line Items] |  |
Fair value option elected aggregate carrying amount, asset | $ 16,000,000 | $ 50,000,000
Mortgage servicing rights | Maximum |  |
Fair Value Measurement Inputs and Valuation Techniques [Line Items] |  |
Difference of internal valuation than dealer marks (as a percent) | 5.00% | 5.00%

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