Fair Value Measurements - Additional Information (Detail) - Level 3 [Member] - Fair Value, Measurements, Nonrecurring [Member] - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impaired real estate assets measured at fair value	$ 2,908	$ 2,785
Senior Unsecured Notes [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of borrowings under senior unsecured notes	$ 328,200	$ 233,500