Annual report pursuant to Section 13 and 15(d)

Mortgages Payable and Debt Maturities - Summary of Mortgage Payable (Detail)

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Mortgages Payable and Debt Maturities - Summary of Mortgage Payable (Detail) - USD ($)
$ in Thousands
Dec. 31, 2017
Dec. 31, 2016
Debt Instrument [Line Items]    
Mortgages payable $ 12,674 $ 13,027
4.98% Mortgage Note Due January 1, 2021 [Member]    
Debt Instrument [Line Items]    
Mortgages payable 2,916 2,966
4.065% Mortgage Note Due April 1, 2023 [Member]    
Debt Instrument [Line Items]    
Mortgages payable 4,119 4,207
5.26% Mortgage Note Due November 1, 2023 [Member]    
Debt Instrument [Line Items]    
Mortgages payable 3,939 4,002
5.99% Mortgage Notes Due May 1, 2026 [Member]    
Debt Instrument [Line Items]    
Mortgages payable $ 1,700 $ 1,852