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Indebtedness - Schedule of Principal Payments (Parenthetical) (Detail) - USD ($)
$ in Thousands
Jun. 30, 2018
Dec. 31, 2017
Debt Instrument [Line Items]    
Mortgage indebtedness $ 1,428,025 $ 641,082
Mortgages indebtedness [Member]    
Debt Instrument [Line Items]    
Mortgage indebtedness $ 1,270,000