Debt - CMBS - Narrative (Details)
$ in Thousands
3 Months Ended
Jan. 22, 2018
USD ($)
Mar. 31, 2018
USD ($)
Property
Loan
loan
Mar. 31, 2017
USD ($)
Dec. 31, 2017
USD ($)
Debt Instrument [Line Items]        
Weighted average stated interest rate, excluding defaulted loans   4.84%    
Unamortized deferred financing costs   $ 38,140   $ 39,572
Capitalized interest   1,062 $ 714  
CMBS Loans        
Debt Instrument [Line Items]        
Unamortized deferred financing costs   4,800   3,900
Unamortized discount   $ 100   $ 100
CMBS Loans | CMBS        
Debt Instrument [Line Items]        
Number of loans secured by mortgage on leased properties and related assets | loan   7    
Number of properties securing borrowings | Property   101    
Number of properties securing loans | Property   3    
Debt default amount   $ 31,400    
Capitalized interest   $ 10,300    
CMBS Loans | CMBS | Minimum        
Debt Instrument [Line Items]        
Stated interest rate   4.67%    
Default interest rate   7.53%    
CMBS Loans | CMBS | Maximum        
Debt Instrument [Line Items]        
Stated interest rate   6.00%    
Default interest rate   9.85%    
Discontinued Operations, Disposed of by Sale | CMBS Loans        
Debt Instrument [Line Items]        
Number of loans in default | Loan   3    
Societe Generale And Barclays Bank PLC | Non-Recourse CMBS Loan Agreement | Loans Payable        
Debt Instrument [Line Items]        
Maturity 10 years      
Proceeds from issuance of debt $ 84,000      
10-year Mid-Market Swap Rate | Societe Generale And Barclays Bank PLC | Non-Recourse CMBS Loan Agreement | Loans Payable        
Debt Instrument [Line Items]        
Basis spread on variable rate 245.00%