Annual report pursuant to Section 13 and 15(d)

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

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Real Estate Dispositions, Held for Sale, and Impairment Charges - Additional Information (Detail)
12 Months Ended
Dec. 31, 2018
USD ($)
property
Dec. 31, 2017
USD ($)
property
Dec. 31, 2016
USD ($)
property
Schedule Of Real Estate Owned Held For Sale [Line Items]      
Number of real estate properties, held for sale 1    
Number of impaired assets, held and used 0    
Impairment charge | $ $ 0 $ 6,835,000 $ 2,016,000
Gain (loss) on sale of real estate, net | $ $ 2,763,000 $ 3,993,000 $ 242,000
Discontinued Operations, Held-for-sale or Disposed of by Sale [Member]      
Schedule Of Real Estate Owned Held For Sale [Line Items]      
Number of impaired assets, held and used     1
Number of impaired assets, sold 1 2 5
Number of impaired assets, held for sale     1
Held-for-sale      
Schedule Of Real Estate Owned Held For Sale [Line Items]      
Number of real estate properties, held for sale 1 2  
Number of impaired assets   3 7