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LOANS - Narrative (Details) | 3 Months Ended |  |
--- | --- | --- | ---
Mar. 31, 2021 USD ($) loan | Mar. 31, 2020 USD ($) | Dec. 31, 2020 USD ($) | Jan. 01, 2020 USD ($)
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items] |  |  |  |  |
Assets | $ 85,369,589,000 |  | $ 88,455,103,000 | [1] |
Loan loss provision recorded during period | (139,620,000) | $ 99,326,000 |  |  |
Allowance for loan loss | $ 33,400,000 |  | 169,500,000 |  |
Minimum |  |  |  |  |
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items] |  |  |  |  |
Senior secured loans, stated maturity (in years) | 5 years |  |  |  |
Maximum |  |  |  |  |
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items] |  |  |  |  |
Senior secured loans, stated maturity (in years) | 7 years |  |  |  |
Cumulative Effect, Period of Adoption, Adjustment |  |  |  |  |
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items] |  |  |  |  |
Allowance for loan loss |  |  | 37,400,000 |  |
Residential Mortgage Loans |  |  |  |  |
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items] |  |  |  |  |
Assets | $ 528,900,000 |  | 345,800,000 |  |
Loans | $ 46,000,000.0 |  | $ 47,000,000.0 |  |
Percent of adjustable-rate loans | 38.00% |  | 37.00% |  |
Commercial Mortgage Loans |  |  |  |  |
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items] |  |  |  |  |
Loan loss provision recorded during period | $ 52,100,000 |  |  |  |
Current period (allowance) reversal | (67,400,000) |  |  |  |
Restructuring, carrying value | $ 243,800,000 |  |  |  |
Number of loans restructured | loan | 5 |  |  |  |
Number of contracts modified, partial paydowns | loan | 2 |  |  |  |
Restructuring, partial paydowns | $ 4,500,000 |  |  |  |
Future funding commitments |  |  | $ 4,100,000 |  |
Loans on nonaccrual status | 46,800,000 |  |  |  |
Interest income, nonaccrual | 2,100,000 |  |  |  |
Unfunded commitments |  |  | $ 99,300,000 |  |
Unfunded commitments, expected credit loss | (5,100,000) |  |  |  |
Loans receivable with variable interest rates |  |  | 94.00% |  |
Commercial Mortgage Loans | Cumulative Effect, Period of Adoption, Adjustment |  |  |  |  |
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items] |  |  |  |  |
Allowance for loan loss |  |  |  |  | $ 7,800,000
Commercial Mortgage Loans | Cumulative Effect, Period of Adoption, Adjusted Balance |  |  |  |  |
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items] |  |  |  |  |
Loan loss provision recorded during period | 23,200,000 |  |  |  |
Current period (allowance) reversal | (62,500,000) |  |  |  |
Commercial Mortgage Loans | Extended Maturity |  |  |  |  |
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items] |  |  |  |  |
Allowance for loan loss | $ 23,600,000 |  |  |  |
Number of loans restructured | loan | 4 |  |  |  |
Commercial Mortgage Loans | Payment Deferral, Forbearance |  |  |  |  |
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items] |  |  |  |  |
Number of loans restructured | loan | 1 |  |  |  |
Forbearance duration | 120 days |  |  |  |
Corporate Loans |  |  |  |  |
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items] |  |  |  |  |
Loan loss provision recorded during period | $ 10,000,000.0 |  |  |  |
Loans | 2,074,475,000 |  | $ 2,239,930,000 |  |
Principal balance | 29,300,000 |  |  |  |
Carrying value | 21,900,000 |  |  |  |
Unfunded commitments | 93,000,000.0 |  | 87,300,000 |  |
Unfunded commitments, expected credit loss | 600,000 |  | 700,000 |  |
Debt | 4,800,000 |  |  |  |
Allowance for loan losses, writeoffs | 11,900,000 |  |  |  |
Corporate Loans | First lien loans |  |  |  |  |
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items] |  |  |  |  |
Loans | 1,431,882,000 |  | 1,489,125,000 |  |
Allowance for loan losses, writeoffs | 19,600,000 |  |  |  |
Corporate Loans | Second lien loans |  |  |  |  |
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items] |  |  |  |  |
Loans | 642,593,000 |  | $ 750,805,000 |  |
Debt | 2,800,000 |  |  |  |
Corporate Loans | Cumulative Effect, Period of Adoption, Adjustment |  |  |  |  |
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items] |  |  |  |  |
Allowance for loan loss |  |  |  |  | $ 29,700,000
Corporate Loans | Cumulative Effect, Period of Adoption, Adjusted Balance |  |  |  |  |
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items] |  |  |  |  |
Loan loss provision recorded during period | $ (6,200,000) | $ 14,100,000 |  |  |
[1] | Derived from the audited consolidated financial statements at December 31, 2020.

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