Annual report pursuant to Section 13 and 15(d)

Properties, net (Details 6)

v3.6.0.2
Properties, net (Details 6)
ft² in Thousands, $ in Thousands
12 Months Ended
Aug. 28, 2015
USD ($)
Dec. 31, 2016
USD ($)
ft²
buillding
Property
Dec. 31, 2015
USD ($)
ft²
buillding
Property
Dec. 31, 2014
USD ($)
ft²
buillding
Property
Dispositions        
(Loss) gain on early extinguishment of debt   $ (1,110) $ 85,275 $ (9,552)
Non-operating Properties [Member]        
Dispositions        
Gain on disposition     4,000 5,600
Sale price of non-operating properties     $ 18,100 $ 28,300
Operating properties, net [Member]        
Dispositions        
Number of Buildings | buillding   21 9 8
Total Rentable Square Feet | ft²   1,577 1,597 303
Transaction Value   $ 248,738 $ 347,785 $ 28,835
Gain on disposition   $ 15,871 $ 64,033 $ 5,093
15000 and 15010 Conference Center Drive [Member] | Operating properties, net [Member]        
Dispositions        
Debt settled through the surrender of real estate assets $ 150,000      
(Loss) gain on early extinguishment of debt $ 84,800      
Regional Office [Member] | Operating properties, net [Member] | 1550 Westbranch Drive [Member]        
Dispositions        
Number of Buildings | buillding     1  
Total Rentable Square Feet | ft²     160  
Transaction Value     $ 27,800  
Gain on disposition     $ 0  
Regional Office [Member] | Operating properties, net [Member] | 13200 Woodland Park Road [Member]        
Dispositions        
Number of Buildings | buillding     1  
Total Rentable Square Feet | ft²     397  
Transaction Value     $ 84,000  
Gain on disposition     $ 42,515  
Regional Office [Member] | Operating properties, net [Member] | 9900, 9910, 9920 Franklin Square Drive [Member]        
Dispositions        
Number of Buildings | buillding     3  
Total Rentable Square Feet | ft²     135  
Transaction Value     $ 24,150  
Gain on disposition     $ 6,468  
Regional Office [Member] | Operating properties, net [Member] | 9690 Deereco Road and 375 W Padonia Road [Member]        
Dispositions        
Number of Buildings | buillding     2  
Total Rentable Square Feet | ft²     240  
Transaction Value     $ 44,500  
Gain on disposition     $ 15,050  
Regional Office [Member] | Operating properties, net [Member] | 4969 and 4979 Mercantile Rd [Member]        
Dispositions        
Number of Buildings | buillding       2
Total Rentable Square Feet | ft²       97
Transaction Value       $ 5,960
Gain on disposition       $ 2,124
Regional Office [Member] | Operating properties, net [Member] | 9930 and 9940 Franklin Square [Member]        
Dispositions        
Number of Buildings | buillding       2
Total Rentable Square Feet | ft²       72
Transaction Value       $ 10,475
Gain on disposition       $ 2,303
Regional Office [Member] | Operating properties, net [Member] | 5020, 5022, 5024 and 5026 Campbell Boulevard [Member]        
Dispositions        
Number of Buildings | buillding       4
Total Rentable Square Feet | ft²       134
Transaction Value       $ 12,400
Gain on disposition       $ 666
Defense/Information Technology Sector [Member] | Northern Virginia Defense/IT [Member] | Operating properties, net [Member] | 15000 and 15010 Conference Center Drive [Member]        
Dispositions        
Number of Buildings | buillding     2  
Total Rentable Square Feet | ft²     665  
Transaction Value     $ 167,335  
Gain on disposition     $ 0  
Newly-constructed properties placed in service [Member]        
Dispositions        
Square Feet of Properties Placed in Service | ft²   639 897 692
Number of real estate properties | Property   6 7 5
Newly Redeveloped Properties Placed In Service [Member]        
Dispositions        
Square Feet of Properties Placed in Service | ft²   61    
Number of real estate properties | Property   3    
Newly Redeveloped Properties Placed In Service [Member] | Greater Philadelphia and St. Mary's County, Maryland [Member]        
Dispositions        
Square Feet of Properties Placed in Service | ft²     170  
Number of real estate properties | Property     2  
Properties under Construction or Contractually Commited for Construction [Member]        
Dispositions        
Total Rentable Square Feet | ft²   1,300    
Number of real estate properties | Property   8    
Properties under redevelopment [Member]        
Dispositions        
Total Rentable Square Feet | ft²   104    
Number of real estate properties | Property   3    
Office properties under, or contractually committed for, construction or approved for redevelopment [Member]        
Dispositions        
Total Rentable Square Feet | ft²   1,400    
Number of real estate properties | Property   11    
Office properties under, or contractually committed for, construction or approved for redevelopment [Member] | Properties completed Held-for-future lease [Member]        
Dispositions        
Number of real estate properties | Property   2    
Office properties under, or contractually committed for, construction or approved for redevelopment [Member] | Partially operational properties [Member]        
Dispositions        
Number of real estate properties | Property   2