Quarterly report pursuant to Section 13 or 15(d)

Real Estate Dispositions, Held for Sale and Impairment Charges - Additional Information (Detail)

v3.10.0.1
Real Estate Dispositions, Held for Sale and Impairment Charges - Additional Information (Detail)
3 Months Ended 9 Months Ended
Sep. 30, 2018
USD ($)
property
Sep. 30, 2017
USD ($)
Sep. 30, 2018
USD ($)
property
Sep. 30, 2017
USD ($)
property
Dec. 31, 2017
property
Real Estate Properties [Line Items]          
Number of properties sold     2    
Number of real estate properties, held for sale 1   1    
Number of impaired assets, held and used 0   0    
Impairment charge | $ $ 0 $ 0 $ 0 $ 3,999,000  
Number of impaired assets sold, held for sale         2
Arlington, Texas and Tewksbury, Massachusetts          
Real Estate Properties [Line Items]          
Number of real estate properties, held for sale         2
Disposed of by sale          
Real Estate Properties [Line Items]          
Number of properties sold     2    
Held for sale          
Real Estate Properties [Line Items]          
Number of impaired assets       2