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LOANS - Additional Information (Details) - USD ($) | 12 Months Ended
--- | ---
Dec. 31, 2019 | Dec. 31, 2018 | Dec. 31, 2017
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items] |  |  |
Assets | $ 130,295,081,000 | $ 105,787,527,000 |
Loan loss provision | 16,569,000 | 3,496,000 | $ 0
Aggregate principal balance | 63,200,000 | 7,000,000.0 |
Carrying value | 43,100,000 | 3,500,000 |
Balance of the loan loss provision | 20,100,000 | $ 3,500,000 |
Loans | $ 669,713,000 |  |
Loans receivable with variable rates of interest | 92.00% | 88.00% |
Residential Mortgage Loans |  |  |
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items] |  |  |
Assets | $ 1,600,000,000 | $ 1,400,000,000 |
Loans | $ 66,700,000 | $ 97,500,000 |
Percent of adjustable-rate loans | 36.00% | 47.00% |
Commercial Mortgage Loans |  |  |
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items] |  |  |
Loans | $ 0 | $ 42,200,000 |
Unfunded corporate loan commitments | 181,400,000 |  |
Corporate Loans |  |  |
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items] |  |  |
Loan loss provision | 7,400,000 |  |
Aggregate principal balance | 19,600,000 |  |
Carrying value | 12,200,000 |  |
Unfunded corporate loan commitments | $ 81,200,000 |  |
Minimum |  |  |
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items] |  |  |
Senior secured loans, stated maturity | 5 years |  |
Maximum |  |  |
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items] |  |  |
Senior secured loans, stated maturity | 7 years |  |

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