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LOANS - Geographic Concentrations Based on Unpaid Principal Balances (Details) - Residential mortgage loans - Geographic Concentration Risk | 12 Months Ended
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Dec. 31, 2019 | Dec. 31, 2018
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items] |  |
Geographic concentrations of residential mortgage loans | 100.00% | 100.00%
California |  |
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items] |  |
Geographic concentrations of residential mortgage loans | 52.10% | 53.70%
New York |  |
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items] |  |
Geographic concentrations of residential mortgage loans | 10.50% | 6.60%
Florida |  |
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items] |  |
Geographic concentrations of residential mortgage loans | 5.30% | 7.10%
Other |  |
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items] |  |
Geographic concentrations of residential mortgage loans | 32.10% | 32.60%

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