Related Party Transactions - Summary of Fees to Vornado (Detail) - Vornado - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Related Party Transaction [Line Items]
Fees to related party	$ 1,641	$ 1,661	$ 3,374	$ 3,388
Company management fees
Related Party Transaction [Line Items]
Fees to related party	700	700	1,400	1,400
Development fees
Related Party Transaction [Line Items]
Fees to related party	2	4	9	32
Leasing fees
Related Party Transaction [Line Items]
Fees to related party	0	4	0	15
Property management, cleaning, engineering and security fees
Related Party Transaction [Line Items]
Fees to related party	$ 939	$ 953	$ 1,965	$ 1,941