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Real Estate Inventories - Additional Information (Detail) - USD ($)
3 Months Ended
Mar. 31, 2018
Mar. 31, 2017
Real Estate Properties [Line Items]    
Impairment charges $ 558,000 $ 0
Washington D.C. [Member]    
Real Estate Properties [Line Items]    
Impairment charges $ 558,000 $ 0