Real Estate Transactions (Schedule Of Property Sales) (Details) (USD $)
 3 Months Ended 6 Months Ended 6 Months Ended 12 Months Ended 6 Months Ended
Jun. 30, 2013
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Jun. 30, 2013
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Jun. 30, 2013
19 Skyline Drive [Member]
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Dec. 31, 2012
19 Skyline Drive [Member]
Jun. 30, 2013
55 Corporate Drive [Member]
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Jun. 30, 2013
200 Riser Road [Member]
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Jun. 30, 2013
777 Passaic Avenue [Member]
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Jun. 30, 2013
16 And 18 Sentry Park West [Member]
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Dec. 31, 2012
16 And 18 Sentry Park West [Member]
Jun. 30, 2013
51 Imclone Drive [Member]
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Jun. 30, 2013
40 Richards Avenue [Member]
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Number of Buildings 8 8 1 [1]   1 1 1 2 [2]   1 [3] 1
Rentable Square Feet 1,210,888 1,210,888 248,400 [1]   204,057 286,628 75,000 188,103 [2]   63,213 [3] 145,487
Net Sales Proceeds   $ 165,513,000 $ 16,131,000 [1]   $ 70,967,000 $ 31,775,000 $ 5,640,000 $ 19,041,000 [2]   $ 6,101,000 [3] $ 15,858,000
Net Book Value 127,904,000 127,904,000 16,005,000 [1]   51,308,000 14,852,000 3,713,000 19,721,000 [2]   5,278,000 [3] 17,027,000
Realized Gain (loss)   37,609,000 126,000 [1]   19,659,000 16,923,000 1,927,000 (680,000) [2]   823,000 [3] (1,169,000)
Valuation allowance       7,100,000              
Note receivable 5,000,000 5,000,000                  
Note receivable, net present value 3,683,000 3,683,000                  
Mortgage loan, maturity period     10 years                
Impairment charge on property 23,851,000 23,851,000             8,400,000    
Loss from early extinguishment of debt $ 703,000 $ 703,000                  
[1] The Company recognized a valuation allowance of $7.1 million on this property at December 31, 2012. In connection with the sale, the Company provided an interest-free note receivable to the buyer of $5 million (with a net present value of $3.7 million at June 30, 2013) which matures in ten years and requires monthly payments of principal. See Note 5: Deferred charges, goodwill and other assets.
[2] The Company recorded an $8.4 million impairment charge on these properties at December 31, 2012. The Company has retained a subordinated interest in these properties.
[3] The property was encumbered by a mortgage loan which was satisfied by the Company at the time of the sale. The Company incurred $0.7 million in costs for the debt satisfaction, which was included in discontinued operations: loss from early retirement of debt for the three and six months ended June 30, 2013.