Recent Transactions (Schedule Of Properties Acquired) (Details)
$ in Thousands
 12 Months Ended
Dec. 31, 2016
USD ($)
ft²
item
Business Acquisition [Line Items]  
Number of Buildings, Acquired | item 5
Rentable Square Feet, Acquired | ft² 1,058,462
Acquisition Cost | $ $ 326,811
11 Martine Avenue [Member]  
Business Acquisition [Line Items]  
Number of Buildings, Acquired | item 1 [1]
Rentable Square Feet, Acquired | ft² 82,000 [1]
Acquisition Cost | $ $ 10,750 [1]
Number of apartment units | item 4
Area of property (in square feet) | ft² 262,000
320, 321 University Avenue [Member]  
Business Acquisition [Line Items]  
Number of Buildings, Acquired | item 2 [2]
Rentable Square Feet, Acquired | ft² 147,406 [2]
Acquisition Cost | $ $ 23,000 [2]
101 Wood Avenue South [Member]  
Business Acquisition [Line Items]  
Number of Buildings, Acquired | item 1 [3]
Rentable Square Feet, Acquired | ft² 262,841 [3]
Acquisition Cost | $ $ 82,300 [3]
111 River Street [Member]  
Business Acquisition [Line Items]  
Number of Buildings, Acquired | item 1 [3]
Rentable Square Feet, Acquired | ft² 566,215 [3]
Acquisition Cost | $ $ 210,761 [3]
[1] Acquisition represented four units of condominium interests which collectively comprise floors 2 through 5. Upon completion of the acquisition, the Company owns the entire 14-story 262,000 square-foot building. The acquisition was funded using available cash.
[2] This acquisition was funded through borrowings under the Company's unsecured revolving credit facility.
[3] This acquisition was funded using available cash and through borrowings under the Company's unsecured revolving credit facility.(a) Above market, in-place and below market leases are being amortized over a weighted-average term of 8.1 years.