XML 59 R49.htm IDEA: XBRL DOCUMENT v3.5.0.2
Equity (Details) - USD ($)
 9 Months Ended
Sep. 30, 2016
Sep. 30, 2015
Dec. 31, 2015
Equity, Class of Treasury Stock      
Share repurchase program, authorized amount     $ 400,000,000.0
Stock Repurchased During Period, Value $ 13,271,000 $ 199,944,000  
Common shares of beneficial interest, par value (in dollars per share) $ 0.01   $ 0.01
Share repurchase program, remaining authorized amount $ 161,542,669    
Common Stock      
Equity, Class of Treasury Stock      
Common shares repurchased and retired (in shares) 610,607 6,992,708  
Stock Repurchased During Period, Value $ 6,000 $ 70,000  
Redemption of Operating Partnership units (in shares) 335,250    
Limited Partners      
Equity, Class of Treasury Stock      
Remaining limited partner ownership interest in Operating Partnership units (in shares) 558,750