Selected Quarterly Financial Data (Unaudited) - Narratives (Details)
3 Months Ended 12 Months Ended
Oct. 26, 2016
Apr. 11, 2016
property
Dec. 31, 2016
USD ($)
property
Sep. 30, 2016
USD ($)
Jun. 30, 2016
USD ($)
Mar. 31, 2016
USD ($)
Dec. 31, 2016
USD ($)
property
Dec. 31, 2015
USD ($)
Dec. 31, 2014
USD ($)
Mar. 31, 2015
USD ($)
Business Acquisition                    
Gain on change in control of interests             $ 49,922,000 $ 0 $ 0  
Number of real estate properties | property     395       395      
Gain on sale of real estate, net of tax             $ 132,858,000 2,197,000 13,338,000  
Loss on extinguishment of debt     $ (800,000) $ (16,000,000) $ (5,100,000) $ (2,500,000) (24,376,000) (275,000) (263,000)  
Impairment charges             29,706,000 1,023,000 570,000  
Equity in earnings of equity method investments in real estate             3,262,000 14,667,000 24,073,000  
Goodwill impairment             0      
Ishops                    
Business Acquisition                    
Deferred gain on the sale of property               2,200,000   $ 2,200,000
Level 3 | Nonrecurring                    
Business Acquisition                    
Impairment charges             31,625,000 $ 1,023,000 $ 1,336,000  
Self storage | Madison Storage NYC, LLC and Veritas Group IX-NYC, LLC                    
Business Acquisition                    
Gain on change in control of interests             49,900,000      
Increase in ownership equity investments 40.00% 15.00%                
Number of real estate properties | property   5                
Gain on sale of real estate, net of tax       $ 82,300,000 $ 25,000,000 $ 25,400,000        
All Other | Shelborne Property Associates, LLC | Third Party                    
Business Acquisition                    
Goodwill impairment             22,800,000      
Contract termination income             10,600,000      
Guaranteed loss compensation             $ 10,600,000