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Real estate asset sales (Details)
3 Months Ended 12 Months Ended
Dec. 31, 2019
USD ($)
ft²
Dec. 31, 2019
USD ($)
ft²
Dec. 31, 2018
USD ($)
Dec. 31, 2017
USD ($)
Jun. 30, 2019
ft²
Real Estate Properties [Line Items]          
Gain on sales of real estate – rental properties   $ 474,000 $ 8,704,000 $ 270,000  
Assets held for sale - area of real estate | ft² 526,006 526,006      
Impairment of real estate   $ 12,334,000 $ 6,311,000 $ 203,000  
6138/6150 Nancy Ridge Drive          
Real Estate Properties [Line Items]          
Area of Real Estate Property | ft²         56,698
Proceeds from Sale of Real Estate $ 6,600,000        
Proceeds from Sale of Real Estate (Per RSF) 117        
Gain on sales of real estate – rental properties $ 474,000