Debt - CMBS - Narrative (Details)
$ in Thousands
3 Months Ended 9 Months Ended
Sep. 30, 2015
USD ($)
Property
loan
Sep. 30, 2014
Property
Sep. 30, 2015
USD ($)
Property
Loan
loan
Sep. 30, 2014
USD ($)
Property
Dec. 31, 2014
USD ($)
Debt Instrument [Line Items]          
Number of properties securing borrowings | Property 145   145    
Capitalized interest     $ 4,686 $ 997  
Number of properties disposed of during period | Property 0 1 2 6  
CMBS Loans          
Debt Instrument [Line Items]          
Unamortized deferred financing costs $ 5,600   $ 5,600   $ 6,400
Debt default amount 25,400   25,400    
Restricted cash $ 3,600   3,600    
Capitalized interest     $ 400    
Number of properties disposed of during period | Property     5    
Number of properties surrendered | Property     1    
CMBS Loans | Disposed of by sale          
Debt Instrument [Line Items]          
Number of properties disposed of during period | Property     4    
CMBS Loans | CMBS - fixed-rate          
Debt Instrument [Line Items]          
Number of loans secured by mortgage on leased properties and related assets | loan 149   149    
Number of properties securing borrowings | Property 468   468    
Number of CMBS loans in default | Loan     4    
Number of properties securing loans | Property 10   10    
Debt default amount $ 80,100   $ 80,100    
Interest added to principal     6,900    
Restricted cash $ 12,200   $ 12,200    
CMBS Loans | CMBS - fixed-rate | Minimum          
Debt Instrument [Line Items]          
Stated Rates 3.90%   3.90%    
Default interest rate 9.67%   9.67%    
CMBS Loans | CMBS - fixed-rate | Maximum          
Debt Instrument [Line Items]          
Stated Rates 8.39%   8.39%    
Default interest rate 10.88%   10.88%    
CMBS Loans | CMBS - variable-rate          
Debt Instrument [Line Items]          
Number of loans secured by mortgage on leased properties and related assets | loan 9   9    
Number of properties securing borrowings | Property 86   86    
Fixed interest rate, interest rate swaps 5.20%   5.20%    
CMBS Loans | CMBS - variable-rate | Minimum          
Debt Instrument [Line Items]          
Stated Rates 3.20%   3.20%    
CMBS Loans | CMBS - variable-rate | Maximum          
Debt Instrument [Line Items]          
Stated Rates 3.60%   3.60%