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
 9 Months Ended 12 Months Ended
Sep. 30, 2017
USD ($)
ft²
item
Dec. 31, 2016
USD ($)
Dec. 31, 2015
USD ($)
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]      
Unrealized losses on rental properties held for sale $ (25,744)    
Net sales proceeds held by qualified intermediary $ 45,300    
Bergen Portfolio [Member] | Notes Receivable 5.0 and 7.0 Interest Rate [Member] | Buyer [Member]      
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]      
Number of extension options | item 3    
Loan extension period 30 days    
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 58    
Rentable Square Feet, Disposed | ft² 4,177,867    
Net Sales Proceeds $ 344,000    
Net Carrying Value 320,368    
Realized Gain (loss)/Unrealized Loss 23,632    
Totals $ (2,112)    
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    
Disposal Group, Not Discontinued Operations [Member] | 400 Chestnut Ridge Road [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 89,200    
Net Sales Proceeds $ 6,891    
Net Carrying Value 7,498    
Realized Gain (loss)/Unrealized Loss $ (607)    
Disposal Group, Not Discontinued Operations [Member] | 140 East Ridgewood Avenue [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 239,680    
Net Sales Proceeds $ 30,201    
Net Carrying Value 30,737    
Realized Gain (loss)/Unrealized Loss $ (536)    
Disposal Group, Not Discontinued Operations [Member] | Bergen Portfolio [Member]      
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]      
Number of Buildings, Disposed | item 5    
Rentable Square Feet, Disposed | ft² 1,061,544    
Net Sales Proceeds [3] $ 86,973    
Net Carrying Value 135,121    
Realized Gain (loss)/Unrealized Loss $ (48,148)    
Disposal Group, Not Discontinued Operations [Member] | Bergen Portfolio [Member] | Buyer [Member]      
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]      
Number of buyers | item 2    
Mortgage loan, maturity date Nov. 01, 2017    
Number of extension options | item 3    
Loan extension period 30 days    
Notes receivable $ 24,800    
Disposal Group, Not Discontinued Operations [Member] | Bergen Portfolio [Member] | Notes Receivable 4.0 Interest Rate [Member] | Buyer [Member]      
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]      
Interest rate 5.00%    
Disposal Group, Not Discontinued Operations [Member] | Bergen Portfolio [Member] | Notes Receivable 4.0 Interest Rate [Member] | Buyer [Member] | Minimum [Member]      
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]      
Interest rate 4.00%    
Disposal Group, Not Discontinued Operations [Member] | Bergen Portfolio [Member] | Notes Receivable 7.0 Interest Rate [Member] | Buyer [Member]      
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]      
Interest rate 7.00%    
Notes receivable $ 40,200    
Disposal Group, Not Discontinued Operations [Member] | Bergen Portfolio [Member] | Notes Receivable 7.0 Interest Rate [Member] | Buyer [Member] | Maximum [Member]      
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]      
Interest rate 7.00%    
Disposal Group, Not Discontinued Operations [Member] | Bergen Portfolio [Member] | Notes Receivable 5.0 and 7.0 Interest Rate [Member] | Buyer [Member]      
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]      
Mortgage loan, maturity date Nov. 01, 2017    
Notes receivable $ 24,800    
Disposal Group, Not Discontinued Operations [Member] | 377 Summerhill Road [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 40,000    
Net Sales Proceeds $ 3,221    
Net Carrying Value 2,172    
Realized Gain (loss)/Unrealized Loss 1,049    
Disposal Group, Not Discontinued Operations [Member] | 700 Executive Boulevard [Member]      
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]      
Net Sales Proceeds [4] 5,717    
Net Carrying Value [4] 970    
Realized Gain (loss)/Unrealized Loss [4] $ 4,747    
Impairments     $ 7,000
Disposal Group, Not Discontinued Operations [Member] | Totowa Portfolio [Member]      
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]      
Number of Buildings, Disposed | item 13    
Rentable Square Feet, Disposed | ft² 499,243    
Net Sales Proceeds $ 63,624    
Net Carrying Value 27,630    
Realized Gain (loss)/Unrealized Loss $ 35,994    
Disposal Group, Not Discontinued Operations [Member] | 890 Mountain Road [Member]      
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]      
Number of Buildings, Disposed | item [5] 1    
Rentable Square Feet, Disposed | ft² [5] 80,000    
Net Sales Proceeds [5] $ 4,852    
Net Carrying Value [5] 6,139    
Realized Gain (loss)/Unrealized Loss [5] (1,287)    
Impairments     $ 4,200
Net sales proceeds held by qualified intermediary $ 5,900    
Disposal Group, Not Discontinued Operations [Member] | 135 Chestnut Ridge Road [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 66,150    
Net Sales Proceeds [6] $ 5,844    
Net Carrying Value 2,929    
Realized Gain (loss)/Unrealized Loss 2,915    
Net sales proceeds held by qualified intermediary $ 15,300    
Disposal Group, Not Discontinued Operations [Member] | Moorestown Portfolio [Member]      
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]      
Number of Buildings, Disposed | item 26    
Rentable Square Feet, Disposed | ft² 1,260,398    
Net Sales Proceeds [7] $ 73,393    
Net Carrying Value 56,186    
Realized Gain (loss)/Unrealized Loss $ 17,207    
[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 sales proceeds from this sale were held by a qualified intermediary, which is noncash and recorded in deferred charges, goodwill and other assets as of September 30, 2017. See Note 5: Deferred Charges, Goodwill and Other Assets, Net.
[3] At closing, the Company provided short term seller financing through mortgage notes receivable to the two separate buyers of $24.8 million and $40.2 million, respectively, with interest rates ranging from 4.0 to 7.0 percent, which mature in November 2017, some with three 30-day extension options. These amounts are noncash components of the net sales proceeds. See Note 5: Deferred Charges, Goodwill and Other Assets, Net.
[4] This disposition is of a ground leased land property.
[5] The Company recorded an impairment charge of $7.0 million on this property during the year ended December 31, 2015.
[6] The Company recorded an impairment charge of $4.2 million on this property during the year ended December 31, 2015. $5.9 million of the sales proceeds from this sale were held by a qualified intermediary, which is noncash and recorded in deferred charges, goodwill and other assets as of September 30, 2017. See Note 5: Deferred Charges, Goodwill and Other Assets, Net.
[7] $15.3 million of the sales proceeds from this sale were held by a qualified intermediary, which is noncash and recorded in deferred charges, goodwill and other assets as of September 30, 2017. See Note 5: Deferred Charges, Goodwill and Other Assets, Net.