Annual report pursuant to Section 13 and 15(d)

Properties, net (Details 3)

v3.6.0.2
Properties, net (Details 3)
$ in Thousands
 12 Months Ended
Dec. 31, 2014
USD ($)
Dec. 31, 2016
USD ($)
Property
Dec. 31, 2015
USD ($)
Property
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]      
Assets held for sale, net   $ 94,654 $ 96,782
Greater Philadelphia [Member]      
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]      
Depreciation expense resulting from useful life change $ 12,900    
Held-for-sale [Member]      
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]      
Properties, net   85,402 90,188
Deferred rent receivable   4,241 2,891
Intangible assets on real estate acquisitions, net   338 1,591
Deferred leasing costs, net   3,636 1,391
Lease incentives, net   1,037 721
Assets held for sale, net   $ 94,654 $ 96,782
Held-for-sale [Member] | Regional Office [Member] | White Marsh, Maryland [Member]      
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]      
Number of land parcels held-for-sale | Property   8 13
Held-for-sale [Member] | Defense/Information Technology Sector [Member] | Northern Virginia Defense/IT [Member]      
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]      
Number of land parcels held-for-sale | Property   1  
Held-for-sale [Member] | Other Segments [Member] | San Antonio [Member]      
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]      
Number of land parcels held-for-sale | Property     2