Organization - Narrative (Details)
$ in Thousands
9 Months Ended
Sep. 30, 2016
USD ($)
Property
Dec. 31, 2015
USD ($)
Property
Summary Of Business And Significant Accounting Policies [Line Items]    
Gross investment in real estate properties and loans | $ $ 8,388,494 $ 8,302,688
Number of real estate properties 2,705 2,629
Owned Properties    
Summary Of Business And Significant Accounting Policies [Line Items]    
Gross investment in real estate properties and loans | $ $ 8,319,276 $ 8,198,685
Number of real estate properties 2,630 2,485
Gross investment in real estate, percentage 99.20%  
Number of owned real estate properties 2,630  
Financed Properties    
Summary Of Business And Significant Accounting Policies [Line Items]    
Gross investment in real estate properties and loans | $ $ 69,218 $ 104,003
Number of real estate properties 75 144
Securing mortgage properties, percentage 0.80%  
Securing mortgage properties 75  
General Partner    
Summary Of Business And Significant Accounting Policies [Line Items]    
Percentage ownership of operating partnership 1.00%  
Limited Partner    
Summary Of Business And Significant Accounting Policies [Line Items]    
Percentage ownership of operating partnership 99.00%