|
Discontinued Operations (Narrative) (Details) (USD $)
|
9 Months Ended | 3 Months Ended | 0 Months Ended | 9 Months Ended | 12 Months Ended | 3 Months Ended | 9 Months Ended | |||
|---|---|---|---|---|---|---|---|---|---|---|
|
Sep. 30, 2012
|
Dec. 31, 2011
|
Mar. 31, 2012
95 Chestnut Ridge Road [Member]
sqft
|
Jul. 25, 2012
95 Chestnut Ridge Road [Member]
sqft
|
Mar. 28, 2012
2200 Renaissance Boulevard [Member]
sqft
|
Sep. 30, 2012
2200 Renaissance Boulevard [Member]
|
Dec. 31, 2010
2200 Renaissance Boulevard [Member]
|
Jun. 30, 2012
Moorestown, New Jersey [Member]
|
Sep. 30, 2012
Moorestown, New Jersey [Member]
|
Mar. 31, 2012
Moorestown, New Jersey [Member]
sqft
|
|
| Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items] | ||||||||||
| Area of property (in square feet) | 47,700 | 47,700 | 174,124 | 222,258 | ||||||
| Mortgage loan face amount | $ 16,200,000 | |||||||||
| Mortgage loan, maturity date | December 1, 2012 | |||||||||
| Impairment charge on property | 9,500,000 | |||||||||
| Gain recorded on disposal of office property | 4,500,000 | |||||||||
| Valuation allowance recognized | 500,000 | 1,600,000 | 1,600,000 | |||||||
| Proceeds from the sale of property | 4,023,000 | |||||||||
| Aggregate book value of real estate properties | 3,793,204,000 | 3,870,607,000 | 18,400,000 | |||||||
| Net accumulated depreciation | $ 1,455,420,000 | $ 1,409,163,000 | $ 8,200,000 | |||||||
| Number of office buildings | 3 | |||||||||
| Number of properties held for sale | 3 |