| Discontinued Operations (Narrative) (Details) (USD $) In Thousands, unless otherwise specified | 9 Months Ended | |
|---|---|---|
| Sep. 30, 2013
 item
 sqft
 property | Dec. 31, 2012
 New Jersey [Member]
 item | |
| Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items] | ||
| Number of properties sold | 24 | 3 | 
| Number of land parcels sold | 3 | |
| Area of property sold | 3,006,409 | |
| Sales proceeds | $ 390,615 | 
| X | ||||||||||
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- Definition Area Of Real Estate Property Sold No definition available. 
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- Definition Number Of Buildings On Properties Sold No definition available. 
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- Definition Number Of Land Parcels Sold No definition available. 
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| X | ||||||||||
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- Details 
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| X | ||||||||||
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- Definition Cash received from the sale of real estate that is held for investment, that is, it is part of an investing activity during the period. Reference 1: http://www.xbrl.org/2003/role/presentationRef 
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