Quarterly report pursuant to Section 13 or 15(d)

Fair Value Measurements (Details 3)

v3.5.0.2
Fair Value Measurements (Details 3)
$ in Thousands
 3 Months Ended 9 Months Ended
Sep. 30, 2016
USD ($)
Jun. 30, 2016
USD ($)
Mar. 31, 2016
USD ($)
Property
Sep. 30, 2015
USD ($)
Sep. 30, 2016
USD ($)
Sep. 30, 2015
USD ($)
Dec. 31, 2015
USD ($)
Assets and liabilities measured at fair value on a non-recurring basis              
Impairment losses $ 27,699     $ 2,307 $ 99,837 $ 3,545  
Assets held for sale, net 161,454       161,454   $ 96,782
Assets held for sale, net              
Assets and liabilities measured at fair value on a non-recurring basis              
Assets held for sale, net 161,454       161,454   96,782
Fort Meade/BW Corridor              
Assets and liabilities measured at fair value on a non-recurring basis              
Number of properties | Property     2        
Fair value measurement on a nonrecurring basis | Assets held for sale, net              
Assets and liabilities measured at fair value on a non-recurring basis              
Properties held-for-sale             $ 96,800
Impairment losses 11,500   $ 2,400        
Assets held for sale, net 161,454 $ 300,600 $ 225,900   161,454    
Fair Values on Measurement Date 127,128       127,128    
Fair value measurement on a nonrecurring basis | Assets held for sale, net | Significant Unobservable Inputs (Level 3)              
Assets and liabilities measured at fair value on a non-recurring basis              
Fair Values on Measurement Date 127,128       $ 127,128    
Fair value measurement on a nonrecurring basis | Assets disposed of by sale              
Assets and liabilities measured at fair value on a non-recurring basis              
Transaction Value 210,700            
Fair value measurement on a nonrecurring basis | Northern Virginia Defense/IT and Fort Meade/BW Corridor | Assets held for sale, net              
Assets and liabilities measured at fair value on a non-recurring basis              
Impairment losses   14,100          
Fair value measurement on a nonrecurring basis | Defense/Information Technology Locations | Fort Meade/BW Corridor | Assets held for sale, net              
Assets and liabilities measured at fair value on a non-recurring basis              
Impairment losses 13,300            
Fair value measurement on a nonrecurring basis | Aberdeen, Maryland | Land in development or held for future development              
Assets and liabilities measured at fair value on a non-recurring basis              
Impairment losses   4,400          
Fair value measurement on a nonrecurring basis | Aberdeen, Maryland | Other Segments | Operating properties, net              
Assets and liabilities measured at fair value on a non-recurring basis              
Impairment losses   34,400          
Fair value measurement on a nonrecurring basis | Frederick, Maryland | Land in development or held for future development              
Assets and liabilities measured at fair value on a non-recurring basis              
Impairment losses   8,200          
Fair value measurement on a nonrecurring basis | Greater Philadelphia, Pennsylvania | Regional Office | Assets held for sale, net              
Assets and liabilities measured at fair value on a non-recurring basis              
Impairment losses   $ 6,200          
Fair value measurement on a nonrecurring basis | White Marsh, Maryland | Assets held for sale, net              
Assets and liabilities measured at fair value on a non-recurring basis              
Impairment losses 10,000            
Fair value measurement on a nonrecurring basis | White Marsh, Maryland | Assets held for sale, net | Land in development or held for future development              
Assets and liabilities measured at fair value on a non-recurring basis              
Impairment losses $ 2,900