Fair Value Measurements (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Financial Assets And Liabilities Measured At Fair Value
Marketable securities	$ 44,646us-gaap_AvailableForSaleSecurities	$ 31,522us-gaap_AvailableForSaleSecurities
Short-term Investments	24,998us-gaap_OtherShortTermInvestments	0us-gaap_OtherShortTermInvestments
Interest rate cap (included in other assets)	11
Total assets	69,655us-gaap_AssetsFairValueDisclosure
Liabilities measured at fair value	0us-gaap_LiabilitiesFairValueDisclosure	0us-gaap_LiabilitiesFairValueDisclosure
Carrying Reported Amount Fair Value Disclosure [Member]
Assets
Cash Equivalents	111,590	184,796
Liabilities
Mortgages Payable	1,032,780	1,049,959
Leasing commissions (included in amounts due to Vornado)	0	42,924
Total liabilities not measured at fair value	1,032,780	1,092,883
Estimate Of Fair Value Fair Value Disclosure [Member]
Assets
Cash Equivalents	111,590	184,796
Liabilities
Mortgages Payable	1,025,000	1,072,000
Leasing commissions (included in amounts due to Vornado)	0	43,000
Total liabilities not measured at fair value	1,025,000	1,115,000
Fair Value, Inputs, Level 1 [Member]
Financial Assets And Liabilities Measured At Fair Value
Marketable securities	44,646	31,522
Short-term Investments	24,998
Interest rate cap (included in other assets)	0
Total assets	69,644
Fair Value, Inputs, Level 2 [Member]
Financial Assets And Liabilities Measured At Fair Value
Marketable securities	0	0
Short-term Investments	0
Interest rate cap (included in other assets)	11
Total assets	11
Fair Value, Inputs, Level 3 [Member]
Financial Assets And Liabilities Measured At Fair Value
Marketable securities	0	0
Short-term Investments	0
Interest rate cap (included in other assets)	0
Total assets	$ 0

Total liabilities not measured at fair value

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Fair value portion of probable future economic benefits obtained or controlled by an entity as a result of past transactions or events.

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Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading.

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Fair value portion of currency on hand as well as demand deposits with banks or financial institutions. Includes other kinds of accounts that have the general characteristics of demand deposits. Also includes short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates.

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Fair value, before effects of master netting arrangements, of a financial asset or other contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes assets elected not to be offset. Excludes assets not subject to a master netting arrangement.

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Fair value of financial and nonfinancial obligations.

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Fair value portion of notes payable.

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Other investments not otherwise specified in the taxonomy that will be realized in a short period of time, usually less than one year or the normal operating cycle, whichever is longer.

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Receivables to be collected from (obligations owed to) related parties, net as of the balance sheet date where one party can exercise control or significant influence over another party; including affiliates, owners or officers and their immediate families, pension trusts, and so forth.

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