Annual report pursuant to Section 13 and 15(d)

TRANSACTIONS WITH AFFILIATES AND AFFILIATED ENTITIES - Narrative (Details)

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TRANSACTIONS WITH AFFILIATES AND AFFILIATED ENTITIES - Narrative (Details)
$ in Thousands
 1 Months Ended 12 Months Ended
Aug. 31, 2017
USD ($)
Sep. 30, 2016
USD ($)
Apr. 30, 2010
USD ($)
security
Dec. 31, 2017
USD ($)
shares
Dec. 31, 2016
USD ($)
shares
Dec. 31, 2015
USD ($)
Related Party Transaction [Line Items]            
Lease term       1 year    
Period management fee earned       12 months    
Manager advisory fee (as percent)       1.50%    
Incentive compensation percentage (as percent)       25.00%    
Simple interest rate in incentive calculation (as percent)       10.00%    
Shares held by Fortress and affiliates in Newcastle (in shares) | shares       6,800,000    
Stock options outstanding (in shares) | shares       5,010,576 5,126,906  
Due to affiliates       $ 1,786 $ 892  
Cash investments made in affiliates or related companies     $ 75,000      
Expected yield (as percent)     22.50%      
Proceeds from notes receivable $ 69,500 $ 109,900        
Interest income       23,162 91,291 $ 95,891
Amount payable to aircraft operator for aircraft charter (less than)       100 100 100
Manager            
Related Party Transaction [Line Items]            
Termination payment       $ (10,700) 0 0
Affiliates            
Related Party Transaction [Line Items]            
Stock options outstanding (in shares) | shares       3,900,000    
Interest income       $ 14,000 $ 39,600 $ 25,800
CDO            
Related Party Transaction [Line Items]            
Number of securities | security     2      
Subprime Mortgage Loans Subject to Call Option | Subprime Portfolio I            
Related Party Transaction [Line Items]            
Servicing fee percentage (as percent)       0.50%    
Loan unpaid principal balance       $ 200,600    
Subprime Mortgage Loans Subject to Call Option | Subprime Portfolio II            
Related Party Transaction [Line Items]            
Loan unpaid principal balance       $ 306,400