Equity Investments in Real Estate - Ownership Interest in Equity Investments (Details) - USD ($)
$ in Thousands
Dec. 31, 2016
Apr. 11, 2016
Dec. 31, 2015
Dec. 31, 2013
Ownership interest in equity investments:        
Equity investments in real estate $ 451,105   $ 514,147  
Net Lease        
Ownership interest in equity investments:        
Equity investments in real estate $ 222,342   240,345  
Net Lease | Third Party | BPS Nevada, LLC        
Ownership interest in equity investments:        
Ownership interest, percentage 15.00%      
Equity investments in real estate $ 23,036   22,007  
Net Lease | WPC | C1000 Logistiek Vastgooed B.V        
Ownership interest in equity investments:        
Ownership interest, percentage 85.00%      
Equity investments in real estate $ 54,621   59,629  
Net Lease | WPC | U-Haul Moving Partners, Inc. and Mercury Partners, LP (c)        
Ownership interest in equity investments:        
Ownership interest, percentage 12.00%      
Equity investments in real estate $ 37,601   39,309  
Net Lease | WPC | Berry Plastics Corporation        
Ownership interest in equity investments:        
Ownership interest, percentage 50.00%      
Equity investments in real estate $ 14,974   16,094  
Net Lease | WPC | Tesco plc        
Ownership interest in equity investments:        
Ownership interest, percentage 49.00%      
Equity investments in real estate $ 10,807   11,849  
Net Lease | WPC | Hellweg Die Profi-Baumärkte GmbH & Co. KG (referred to as Hellweg 2)        
Ownership interest in equity investments:        
Ownership interest, percentage 37.00%      
Equity investments in real estate $ 10,125   12,212  
Net Lease | WPC | Eroski Sociedad Cooperativa - Mallorca        
Ownership interest in equity investments:        
Ownership interest, percentage 30.00%      
Equity investments in real estate $ 6,576   6,790  
Net Lease | WPC | Dick’s Sporting Goods, Inc.        
Ownership interest in equity investments:        
Ownership interest, percentage 45.00%      
Equity investments in real estate $ 4,367   5,055  
Net Lease | CPA 18 - Global | Bank Pekao S.A.        
Ownership interest in equity investments:        
Ownership interest, percentage 50.00%      
Equity investments in real estate $ 23,025   25,785  
Net Lease | CPA 18 - Global | State Farm        
Ownership interest in equity investments:        
Ownership interest, percentage 50.00%      
Equity investments in real estate $ 17,603   18,587  
Net Lease | CPA 18 - Global | Apply Sorco        
Ownership interest in equity investments:        
Ownership interest, percentage 49.00%      
Equity investments in real estate $ 12,528   15,170  
Net Lease | CPA 18 - Global | Agorkor (referred to as Agrokor 5)        
Ownership interest in equity investments:        
Ownership interest, percentage 20.00%      
Equity investments in real estate $ 7,079   7,858  
Self-Storage        
Ownership interest in equity investments:        
Equity investments in real estate 0   $ 16,060  
Self-Storage | Madison Storage NYC, LLC and Veritas Group IX-NYC, LLC        
Ownership interest in equity investments:        
Ownership interest, percentage   100.00% 45.00% 45.00%
Self-Storage | Third Party | Madison Storage NYC, LLC and Veritas Group IX-NYC, LLC        
Ownership interest in equity investments:        
Equity investments in real estate 0   $ 16,060  
All Other        
Ownership interest in equity investments:        
Equity investments in real estate $ 228,763   257,742  
All Other | Third Party | Shelborne Property Associates, LLC        
Ownership interest in equity investments:        
Ownership interest, percentage 33.00%      
Equity investments in real estate $ 127,424   148,121  
All Other | Third Party | IDL Wheel Tenant, LLC        
Ownership interest in equity investments:        
Equity investments in real estate $ 37,124   44,387  
All Other | Third Party | BG LLH, LLC        
Ownership interest in equity investments:        
Ownership interest, percentage 7.00%      
Equity investments in real estate $ 36,756   37,720  
All Other | Third Party | BPS Nevada, LLC Preferred Equity        
Ownership interest in equity investments:        
Equity investments in real estate $ 27,459   $ 27,514