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Discontinued Operations (Narrative) (Details) (USD $)
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9 Months Ended | 3 Months Ended | 0 Months Ended | 9 Months Ended | 12 Months Ended | 3 Months Ended | 9 Months Ended | |||
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Sep. 30, 2012
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Dec. 31, 2011
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Mar. 31, 2012
95 Chestnut Ridge Road [Member]
sqft
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Jul. 25, 2012
95 Chestnut Ridge Road [Member]
sqft
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Mar. 28, 2012
2200 Renaissance Boulevard [Member]
sqft
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Sep. 30, 2012
2200 Renaissance Boulevard [Member]
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Dec. 31, 2010
2200 Renaissance Boulevard [Member]
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Jun. 30, 2012
Moorestown, New Jersey [Member]
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Sep. 30, 2012
Moorestown, New Jersey [Member]
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Mar. 31, 2012
Moorestown, New Jersey [Member]
sqft
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| 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 |
| X | ||||||||||
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- Definition
Mortgage Loan Maturity Period No definition available.
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| X | ||||||||||
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- Definition
Number Of Properties Held For Sale No definition available.
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| X | ||||||||||
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- Definition
Area of a real estate property. No definition available.
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| X | ||||||||||
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- Definition
The charge against earnings resulting from the aggregate write down of all assets from their carrying value to their fair value. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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| X | ||||||||||
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- Definition
The difference between the carrying value and the sale price of real estate or properties that were intended to be sold or held for capital appreciation or rental income. This element refers to the gain (loss) included in earnings and not to the cash proceeds of the sale. This element is a noncash adjustment to net income when calculating net cash generated by operating activities using the indirect method. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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- Details
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| X | ||||||||||
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- Definition
Amount of the contractual principal due at the origination of the mortgage loan (face amount). Reference 1: http://www.xbrl.org/2003/role/presentationRef
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- Definition
The number of real estate properties owned as of the balance sheet date. No definition available.
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| X | ||||||||||
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- Definition
Cash received for the sale of real estate that is not part of an investing activity during the current period. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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| X | ||||||||||
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- Definition
The cumulative amount of depreciation for real estate property held for investment purposes. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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| X | ||||||||||
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- Definition
Amount of real estate investment property, net of accumulated depreciation, which may include the following: (1) land available-for-sale; (2) land available-for-development; (3) investments in building and building improvements; (4) tenant allowances; (5) developments in-process; (6) rental properties; and (7) other real estate investments. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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| X | ||||||||||
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- Definition
Amount of the valuation allowance for real estate owned that was applied in the period against the carrying amount of real estate owned that was sold, written down or written off. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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