Fair Value Measurements (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013
Financial Assets And Liabilities Measured At Fair Value
Marketable securities	$ 33,363	$ 31,522
Interest rate cap (included in other assets)	242
Total assets	33,605
Carrying Reported Amount Fair Value Disclosure [Member]
Assets
Cash Equivalents	341,294	184,796
Liabilities
Mortgages Payable	1,035,022	1,049,959
Leasing commissions (included in amounts due to Vornado)	42,102	42,924
Total liabilities not measured at fair value	1,077,124	1,092,883
Estimate Of Fair Value Fair Value Disclosure [Member]
Assets
Cash Equivalents	341,294	184,796
Liabilities
Mortgages Payable	1,055,000	1,072,000
Leasing commissions (included in amounts due to Vornado)	42,000	43,000
Total liabilities not measured at fair value	1,097,000	1,115,000
Fair Value, Inputs, Level 1 [Member]
Financial Assets And Liabilities Measured At Fair Value
Marketable securities	33,363	31,522
Interest rate cap (included in other assets)	0
Total assets	33,363
Fair Value, Inputs, Level 2 [Member]
Financial Assets And Liabilities Measured At Fair Value
Marketable securities	0	0
Interest rate cap (included in other assets)	242
Total assets	242
Fair Value, Inputs, Level 3 [Member]
Financial Assets And Liabilities Measured At Fair Value
Marketable securities	0	0
Interest rate cap (included in other assets)	0
Total assets	$ 0