Related Party Transactions (Fees to Vornado) (Details) - Vornado - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Summary of fees to Vornado
Fees to related party (in US dollars)	$ 1,727	$ 8,317
Company management fees
Summary of fees to Vornado
Fees to related party (in US dollars)	700	700
Development fees
Summary of fees to Vornado
Fees to related party (in US dollars)	28	44
Leasing Fees
Summary of fees to Vornado
Fees to related party (in US dollars)	11	6,458
Property Management Fees
Summary of fees to Vornado
Fees to related party (in US dollars)	$ 988	$ 1,115