Annual report pursuant to Section 13 and 15(d)

Fair Value Measurements (Details 3)

v3.10.0.1
Fair Value Measurements (Details 3)
$ in Thousands
3 Months Ended 12 Months Ended
Dec. 31, 2018
USD ($)
Sep. 30, 2018
USD ($)
Jun. 30, 2018
USD ($)
Mar. 31, 2018
USD ($)
Dec. 31, 2017
USD ($)
Sep. 30, 2017
USD ($)
Jun. 30, 2017
USD ($)
Mar. 31, 2017
USD ($)
Dec. 31, 2016
USD ($)
Sep. 30, 2016
USD ($)
Jun. 30, 2016
USD ($)
Mar. 31, 2016
USD ($)
Property
Dec. 31, 2018
USD ($)
Dec. 31, 2017
USD ($)
Dec. 31, 2016
USD ($)
Dec. 31, 2015
USD ($)
Fair value of impaired properties and other assets                                
Assets held for sale, net $ 0       $ 42,226               $ 0 $ 42,226    
Impairment losses                         2,367 15,123 $ 101,391  
Revenues from real estate operations $ 138,482 $ 137,411 $ 146,743 $ 155,476 164,567 $ 157,017 $ 151,435 $ 139,801         $ 578,112 612,820 574,328  
Held-for-sale [Member]                                
Fair value of impaired properties and other assets                                
Assets held for sale, net         42,226                 42,226    
Fort Meade/BW Corridor [Member]                                
Fair value of impaired properties and other assets                                
Number of properties | Property                       2        
Fair value measurement on a nonrecurring basis [Member] | Held-for-sale [Member]                                
Fair value of impaired properties and other assets                                
Assets held for sale, net                 $ 94,700 $ 161,500 $ 300,600 $ 225,900     $ 94,700 $ 96,800
Impairment losses                   11,500   $ 2,400        
Fair value measurement on a nonrecurring basis [Member] | Disposed of by sale [Member]                                
Fair value of impaired properties and other assets                                
Impairment losses                 300              
Fair value measurement on a nonrecurring basis [Member] | Operating properties, net [Member]                                
Fair value of impaired properties and other assets                                
Assets         3,850                 3,850    
Fair value measurement on a nonrecurring basis [Member] | Operating properties, net [Member] | Fair Value, Inputs, Level 3 [Member]                                
Fair value of impaired properties and other assets                                
Assets         3,850                 3,850    
Fair value measurement on a nonrecurring basis [Member] | Projects in development or held for future development [Member]                                
Fair value of impaired properties and other assets                                
Assets         1,755                 1,755    
Fair value measurement on a nonrecurring basis [Member] | Projects in development or held for future development [Member] | Fair Value, Inputs, Level 3 [Member]                                
Fair value of impaired properties and other assets                                
Assets         1,755                 $ 1,755    
Fair value measurement on a nonrecurring basis [Member] | Northern Virginia Defense/IT and Fort Meade/Baltimore Washington Corridor [Member] | Held-for-sale [Member]                                
Fair value of impaired properties and other assets                                
Impairment losses                     14,100          
Fair value measurement on a nonrecurring basis [Member] | Defense/Information Technology Sector [Member] | Northern Virginia Defense/IT [Member] | Held-for-sale [Member]                                
Fair value of impaired properties and other assets                                
Impairment losses                   13,300            
Fair value measurement on a nonrecurring basis [Member] | Aberdeen, Maryland [Member] | Land in development or held for future development [Member]                                
Fair value of impaired properties and other assets                                
Impairment of long-lived assets         4,700                      
Impairment losses                     4,400          
Fair value measurement on a nonrecurring basis [Member] | Aberdeen, Maryland [Member] | Other Segments [Member]                                
Fair value of impaired properties and other assets                                
Impairment of long-lived assets         $ 9,000                      
Fair value measurement on a nonrecurring basis [Member] | Frederick, Maryland [Member] | Land in development or held for future development [Member]                                
Fair value of impaired properties and other assets                                
Impairment losses                     8,200          
Fair value measurement on a nonrecurring basis [Member] | Greater Philadelphia [Member] | Regional Office [Member] | Held-for-sale [Member]                                
Fair value of impaired properties and other assets                                
Impairment losses                     6,200          
Fair value measurement on a nonrecurring basis [Member] | Colorado Springs, Colorado and White Marsh, Maryland [Member] | Regional Office [Member] | Held-for-sale [Member]                                
Fair value of impaired properties and other assets                                
Impairment losses                     2,400          
Fair value measurement on a nonrecurring basis [Member] | White Marsh, Maryland [Member] | Held-for-sale [Member]                                
Fair value of impaired properties and other assets                                
Impairment of long-lived assets             $ 1,600                  
Impairment losses                 1,300 10,000            
Fair value measurement on a nonrecurring basis [Member] | White Marsh, Maryland [Member] | Held-for-sale [Member] | Land in development or held for future development [Member]                                
Fair value of impaired properties and other assets                                
Impairment losses                   2,900            
Operating properties, net [Member] | Fair value measurement on a nonrecurring basis [Member] | Aberdeen, Maryland [Member] | Other Segments [Member]                                
Fair value of impaired properties and other assets                                
Impairment losses                     $ 34,400          
Property Sales [Member] | Fair value measurement on a nonrecurring basis [Member] | Disposed of by sale [Member]                                
Fair value of impaired properties and other assets                                
Revenues from real estate operations                 $ 54,100 $ 210,700