Related Party Transactions - Summary of Fees to Vornado (Detail) - Vornado - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Related Party Transaction [Line Items]
Fees to related party	$ 1,733	$ 1,727
Company management fees
Related Party Transaction [Line Items]
Fees to related party	700	700
Development fees
Related Party Transaction [Line Items]
Fees to related party	7	28
Leasing fees
Related Party Transaction [Line Items]
Fees to related party	0	11
Property management, cleaning, engineering and security fees
Related Party Transaction [Line Items]
Fees to related party	$ 1,026	$ 988