Annual report pursuant to Section 13 and 15(d)

Recent Transactions (Schedule Of Dispositions/Rental Property Held For Sale) (Details)

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Recent Transactions (Schedule Of Dispositions/Rental Property Held For Sale) (Details)
$ in Thousands
 3 Months Ended 12 Months Ended
Dec. 31, 2015
USD ($)
ft²
Sep. 30, 2015
USD ($)
 [1]
Dec. 31, 2016
USD ($)
item
Dec. 31, 2015
USD ($)
ft²
item
Dec. 31, 2013
USD ($)
Dec. 31, 2012
USD ($)
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]            
Number of Buildings, Disposed | item     30 6    
Rentable Square Feet, Disposed | ft² 690,315     690,315    
Net Sales Proceeds     $ 664,481 $ 148,256    
Net Book Value     547,150 94,995    
Realized Gain (loss)/Unrealized Losses, net     117,331 53,261    
Mortgage loans, carrying amount $ 59,700     59,700    
Unrealized losses on properties held for sale     (7,665)      
Totals     $ 109,666      
Impairments $ 33,743 [1] $ 164,176   197,919 $ 25,200  
2 Independence Way [Member]            
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]            
Number of Buildings, Disposed | item [2]     1      
Net Sales Proceeds [2]     $ 4,119      
Net Book Value [2]     4,283      
Realized Gain (loss)/Unrealized Losses, net [2]     $ (164)      
Impairments       3,200    
1201 Connecticut Avenue NW [Member]            
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]            
Number of Buildings, Disposed | item     1      
Net Sales Proceeds     $ 90,591      
Net Book Value     31,827      
Realized Gain (loss)/Unrealized Losses, net     $ 58,764      
125 Broad Street [Member]            
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]            
Number of Buildings, Disposed | item [3]     1      
Net Sales Proceeds [3]     $ 192,323      
Net Book Value [3]     200,183      
Realized Gain (loss)/Unrealized Losses, net [3]     $ (7,860)      
Impairments       83,200    
9200 Edmonston Road [Member]            
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]            
Number of Buildings, Disposed | item     1      
Net Sales Proceeds [4]     $ 4,083      
Net Book Value     3,837      
Realized Gain (loss)/Unrealized Losses, net     $ 246      
Impairments           $ 3,000
1400 L Street [Member]            
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]            
Number of Buildings, Disposed | item     1      
Net Sales Proceeds     $ 68,399      
Net Book Value     30,053      
Realized Gain (loss)/Unrealized Losses, net     $ 38,346      
600 Parsippany Road [Member]            
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]            
Number of Buildings, Disposed | item     1      
Net Sales Proceeds [5]     $ 10,465      
Net Book Value     5,875      
Realized Gain (loss)/Unrealized Losses, net     $ 4,590      
4, 5, 6 Century Drive [Member]            
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]            
Number of Buildings, Disposed | item [6]     3      
Net Sales Proceeds [6]     $ 14,533      
Net Book Value [6]     17,308      
Realized Gain (loss)/Unrealized Losses, net [6]     $ (2,775)      
Impairments       9,800    
Andover Place [Member]            
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]            
Number of Buildings, Disposed | item     1      
Net Sales Proceeds     $ 39,863      
Net Book Value     37,150      
Realized Gain (loss)/Unrealized Losses, net     $ 2,713      
222, 233 Mount Airy Road [Member]            
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]            
Number of Buildings, Disposed | item [7]     2      
Net Sales Proceeds [7]     $ 8,817      
Net Book Value [7]     9,039      
Realized Gain (loss)/Unrealized Losses, net [7]     $ (222)      
Impairments       1,000    
10 Mountainview Road [Member]            
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]            
Number of Buildings, Disposed | item     1      
Net Sales Proceeds     $ 18,990      
Net Book Value     19,571      
Realized Gain (loss)/Unrealized Losses, net     $ (581)      
100 Willowbrook, 2, 3, 4 Paragon [Member]            
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]            
Number of Buildings, Disposed | item [8]     4      
Net Sales Proceeds [8]     $ 14,634      
Net Book Value [8]     19,377      
Realized Gain (loss)/Unrealized Losses, net [8]     $ (4,743)      
Impairments       7,400    
4 Becker Farm Road [Member]            
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]            
Number of Buildings, Disposed | item     1      
Net Sales Proceeds [9]     $ 41,400      
Net Book Value     31,001      
Realized Gain (loss)/Unrealized Losses, net     $ 10,399      
101, 103, 105 Eisenhower Parkway [Member]            
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]            
Number of Buildings, Disposed | item     3      
Net Sales Proceeds     $ 46,423      
Net Book Value     45,999      
Realized Gain (loss)/Unrealized Losses, net     $ 424      
Capital Office Park, Ivy Lane [Member]            
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]            
Number of Buildings, Disposed | item [10]     6      
Net Sales Proceeds [10]     $ 46,570      
Net Book Value [10]     65,064      
Realized Gain (loss)/Unrealized Losses, net [10]     $ (18,494)      
Impairments       66,500    
100 Walnut Avenue [Member]            
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]            
Number of Buildings, Disposed | item     1      
Net Sales Proceeds     $ 28,428      
Net Book Value     7,529      
Realized Gain (loss)/Unrealized Losses, net     $ 20,899      
20 Commerce Drive [Member]            
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]            
Number of Buildings, Disposed | item     1      
Net Sales Proceeds     $ 28,878      
Net Book Value     13,071      
Realized Gain (loss)/Unrealized Losses, net     $ 15,807      
4200 Parliament Place [Member]            
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]            
Number of Buildings, Disposed | item [11]     1      
Net Sales Proceeds [11]     $ 5,965      
Net Book Value [11]     5,983      
Realized Gain (loss)/Unrealized Losses, net [11]     $ (18)      
Impairments       $ 4,200    
1451 Metropolitan Drive [Member]            
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]            
Number of Buildings, Disposed | item       1    
Rentable Square Feet, Disposed | ft² 21,600     21,600    
Net Sales Proceeds       $ 1,072    
Net Book Value       929    
Realized Gain (loss)/Unrealized Losses, net       $ 143    
10 Independence [Member]            
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]            
Number of Buildings, Disposed | item       1    
Rentable Square Feet, Disposed | ft² 120,528     120,528    
Net Sales Proceeds       $ 18,351    
Net Book Value       15,114    
Realized Gain (loss)/Unrealized Losses, net       $ 3,237    
4 Sylvan Way [Member]            
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]            
Number of Buildings, Disposed | item       1    
Rentable Square Feet, Disposed | ft² 105,135     105,135    
Net Sales Proceeds       $ 15,961    
Net Book Value       9,522    
Realized Gain (loss)/Unrealized Losses, net       $ 6,439    
14 Sylvan Way [Member]            
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]            
Number of Buildings, Disposed | item       1    
Rentable Square Feet, Disposed | ft² 203,506     203,506    
Net Sales Proceeds       $ 79,977    
Net Book Value       55,253    
Realized Gain (loss)/Unrealized Losses, net       $ 24,724    
210 Clay Ave [Member]            
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]            
Number of Buildings, Disposed | item       1    
Rentable Square Feet, Disposed | ft² 121,203     121,203    
Net Sales Proceeds       $ 14,766    
Net Book Value       5,202    
Realized Gain (loss)/Unrealized Losses, net       $ 9,564    
5 Becker [Member]            
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]            
Number of Buildings, Disposed | item       1    
Rentable Square Feet, Disposed | ft² 118,343     118,343    
Net Sales Proceeds       $ 18,129    
Net Book Value       8,975    
Realized Gain (loss)/Unrealized Losses, net       $ 9,154    
[1] Amounts for the year ended December 31, 2015 relate to impairment charges as further described in Note 3: Recent Transactions - Impairments on Properties Held and Used.
[2] The Company recorded an impairment charge of $3.2 million on this property during the year ended December 31, 2015.
[3] The Company recorded impairment charges of $83.2 million on this property during the year ended December 31, 2015.
[4] The Company transferred the deed for this property to the lender in satisfaction of its obligations. The Company recorded an impairment charge of $3.0 million on this property during the year ended December 31, 2012.
[5] $10.5 million of the net sales proceeds from this sale were held by a qualified intermediary. The Company received these proceeds on January 11, 2017.
[6] The Company recorded impairment charges of $9.8 million on these properties during the year ended December 31, 2015.
[7] The Company recorded impairment charges of $1.0 million on these properties during the year ended December 31, 2015.
[8] The Company recorded impairment charges of $7.4 million on these properties during the year ended December 31, 2015.
[9] The Company transferred the deed for this property to the lender in satisfaction of its obligations.
[10] The Company recorded impairment charges of $66.5 million on these properties during the year ended December 31, 2015.
[11] The Company recorded an impairment charge of $4.2 million on this property during the year ended December 31, 2015.