Related Party Transactions - Summary of Fees to Vornado (Detail) - Vornado - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Related Party Transaction [Line Items]
Fees to related party	$ 1,742	$ 1,709	$ 5,116	$ 5,097
Company management fees
Related Party Transaction [Line Items]
Fees to related party	700	700	2,100	2,100
Development fees
Related Party Transaction [Line Items]
Fees to related party	17	0	26	32
Leasing fees
Related Party Transaction [Line Items]
Fees to related party	13	3	13	18
Property management, cleaning, engineering and security fees
Related Party Transaction [Line Items]
Fees to related party	$ 1,012	$ 1,006	$ 2,977	$ 2,947