Annual report pursuant to Section 13 and 15(d)

REAL ESTATE AND OTHER SECURITIES - Summary of Real Estate Securities in an Unrealized Loss Position (Details)

v3.20.4
REAL ESTATE AND OTHER SECURITIES - Summary of Real Estate Securities in an Unrealized Loss Position (Details)
$ in Thousands
12 Months Ended
Dec. 31, 2020
USD ($)
security
Dec. 31, 2019
USD ($)
Dec. 31, 2018
USD ($)
Dec. 31, 2017
USD ($)
Debt Securities, Available-for-sale [Line Items]        
Outstanding Face Amount $ 31,869,682 $ 36,159,591    
Credit Impairment - Amortized Cost Basis   (59,063) $ (52,803) $ (23,821)
Amortized Cost Basis $ 14,105,251 $ 18,782,175    
Weighted Average Life (Years) 2 years 2 months 12 days      
Less than 12 Months        
Debt Securities, Available-for-sale [Line Items]        
Outstanding Face Amount $ 7,134,953      
Before Impairment - Amortized Cost Basis 217,955      
Credit Impairment - Amortized Cost Basis (1,776)      
Amortized Cost Basis 216,179      
Gross Unrealized Losses - Less than Twelve Months (28,594)      
Carrying Value - Less than Twelve Months $ 187,585      
Number of Securities - Less than Twelve Months | security 61      
Weighted Average Rating AA+      
Weighted Average Coupon 2.29%      
Weighted Average Yield 4.58%      
Weighted Average Life (Years) 5 years 6 months      
12 or More Months        
Debt Securities, Available-for-sale [Line Items]        
Outstanding Face Amount $ 4,063,623      
Before Impairment - Amortized Cost Basis 143,681      
Credit Impairment - Amortized Cost Basis (6,896)      
Amortized Cost Basis 136,785      
Gross Unrealized Losses - Twelve or More Months (32,223)      
Carrying Value - Twelve or More Months $ 104,562      
Number of Securities - Twelve or More Months | security 80      
Weighted Average Rating AA+      
Weighted Average Coupon 1.56%      
Weighted Average Yield 1.76%      
Weighted Average Life (Years) 4 years 2 months 12 days      
Total/Weighted Average        
Debt Securities, Available-for-sale [Line Items]        
Outstanding Face Amount $ 11,198,576      
Before Impairment - Amortized Cost Basis 361,636      
Credit Impairment - Amortized Cost Basis (8,672)      
Amortized Cost Basis 352,964      
Gross Unrealized Losses - Total/Weighted Average (60,817)      
Carrying Value - Total/Weighted Average $ 292,147      
Number of Securities - Total/Weighted Average | security 141      
Weighted Average Rating AA+      
Weighted Average Coupon 2.00%      
Weighted Average Yield 3.49%      
Weighted Average Life (Years) 5 years