Quarterly report pursuant to Section 13 or 15(d)

Fair Value Measurements (Details 3)

v3.5.0.2
Fair Value Measurements (Details 3) - USD ($)
$ in Thousands
 3 Months Ended 6 Months Ended
Jun. 30, 2016
Jun. 30, 2015
Jun. 30, 2016
Jun. 30, 2015
Assets and liabilities measured at fair value on a non-recurring basis        
Impairment losses $ 69,692 $ 1,238 $ 72,138 $ 1,238
Fair value measurement on a recurring basis        
Assets and liabilities measured at fair value on a non-recurring basis        
Assets 5,046   5,046  
Fair value measurement on a nonrecurring basis | Projects in development or held for future development        
Assets and liabilities measured at fair value on a non-recurring basis        
Assets 9,117   9,117  
Fair value measurement on a nonrecurring basis | Projects in development or held for future development | Significant Unobservable Inputs (Level 3)        
Assets and liabilities measured at fair value on a non-recurring basis        
Assets 9,117   9,117  
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 | 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 | Colorado Springs | Assets held for sale, net        
Assets and liabilities measured at fair value on a non-recurring basis        
Impairment losses     3,400  
Fair value measurement on a nonrecurring basis | White Marsh, Maryland | Regional Office | Assets held for sale, net        
Assets and liabilities measured at fair value on a non-recurring basis        
Impairment losses     1,400  
Assets held for sale, net | Fair value measurement on a nonrecurring basis        
Assets and liabilities measured at fair value on a non-recurring basis        
Assets 55,322   55,322  
Assets held for sale, net | Fair value measurement on a nonrecurring basis | Significant Unobservable Inputs (Level 3)        
Assets and liabilities measured at fair value on a non-recurring basis        
Assets 55,322   55,322  
Operating properties, net | Fair value measurement on a nonrecurring basis        
Assets and liabilities measured at fair value on a non-recurring basis        
Assets 13,700   13,700  
Operating properties, net | Fair value measurement on a nonrecurring basis | Significant Unobservable Inputs (Level 3)        
Assets and liabilities measured at fair value on a non-recurring basis        
Assets $ 13,700   $ 13,700