Quarterly report pursuant to Section 13 or 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
 6 Months Ended 12 Months Ended
Jun. 30, 2017
USD ($)
ft²
item
Dec. 31, 2016
USD ($)
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]    
Net Sales Proceeds $ 63,284  
Net Carrying Value 50,986  
Realized Gain (loss)/Unrealized Loss 12,298  
Unrealized losses on rental properties held for sale $ (45,746)  
Disposal Group, Not Discontinued Operations [Member]    
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]    
Number of Buildings, Disposed | item 9  
Rentable Square Feet, Disposed | ft² 841,652  
Net Sales Proceeds $ 63,284  
Net Carrying Value 50,986  
Totals $ (33,448)  
Disposal Group, Not Discontinued Operations [Member] | Cranford Portfolio [Member]    
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]    
Number of Buildings, Disposed | item 6  
Rentable Square Feet, Disposed | ft² 435,976  
Net Sales Proceeds $ 26,598  
Net Carrying Value 22,736  
Realized Gain (loss)/Unrealized Loss $ 3,862  
Disposal Group, Not Discontinued Operations [Member] | 440 Route 22 East [Member]    
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]    
Number of Buildings, Disposed | item [1] 1  
Rentable Square Feet, Disposed | ft² [1] 198,376  
Net Sales Proceeds [1] $ 10,074  
Net Carrying Value [1] 10,069  
Realized Gain (loss)/Unrealized Loss [1] $ 5  
Impairments   $ 7,700
Disposal Group, Not Discontinued Operations [Member] | 3 Independence 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 111,300  
Net Sales Proceeds $ 11,549  
Net Carrying Value 9,910  
Realized Gain (loss)/Unrealized Loss $ 1,639  
Disposal Group, Not Discontinued Operations [Member] | 103 Carnegie Center [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 96,000  
Net Sales Proceeds [2] $ 15,063  
Net Carrying Value 8,271  
Realized Gain (loss)/Unrealized Loss 6,792  
Net sales proceeds held by qualified intermediary $ 15,100  
[1] The Company recorded a valuation allowance of $7.7 million on this property during the year ended December 31, 2016.
[2] $15.1 million of the net sales proceeds from this sale were held by a qualified intermediary.