Stock-based Compensation (Vornado Restricted Stock or Restricted Operating Partnership Units Narrative) (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation expense	$ 32,829	$ 33,980	$ 39,846
Restricted Stock Units RSU
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period (years)	4 years
Share-based compensation expense	$ 729	851	837
Compensation cost not yet recognized	$ 860
Compensation cost not yet recognized, period for recognition	1 year 8 months
Share Based Compensation Equity Instruments Other Than Stock Options And Restricted Stock Units Summary
Grant-date fair value	$ 601	927	906
Vested in period, fair value	645	641	882
Dividends, share-based compensation	$ 46	56	58
Restricted Operating Partnership Units Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period (years)	4 years
Share-based compensation expense	$ 20,630	21,136	22,180
Compensation cost not yet recognized	$ 18,229
Compensation cost not yet recognized, period for recognition	1 year 9 months
Share Based Compensation Equity Instruments Other Than Stock Options And Restricted Stock Units Summary
Grant-date fair value	$ 24,927	18,492	20,293
Vested in period, fair value	20,903	22,701	20,072
Dividends, share-based compensation	$ 2,310	$ 1,968	$ 2,414

Represents the expense recognized during the period arising from equity-based compensation arrangements (for example, shares of stock, unit, stock options or other equity instruments) with employees, directors and certain consultants qualifying for treatment as employees.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SAB Topic 14.F)
-URI http://asc.fasb.org/extlink&oid=27013229&loc=d3e301413-122809

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
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-Section 50
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Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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-Section 50
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Amount of paid and unpaid cash, stock, and paid-in-kind (PIK) dividends declared and applicable to holders of share-based compensation, for example, but not limited to, non-vested shares, stock options, or restricted stock units.

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Unrecognized cost of unvested share-based compensation awards.

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-Publisher FASB
-Name Accounting Standards Codification
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Weighted average period over which unrecognized compensation is expected to be recognized for equity-based compensation plans, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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Period which an employee's right to exercise an award is no longer contingent on satisfaction of either a service condition, market condition or a performance condition, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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Fair value of share-based awards for which the grantee gained the right by satisfying service and performance requirements, to receive or retain shares or units, other instruments, or cash.

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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The fair value at grant date for equity-based awards issued during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

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