Stock-based Compensation (Vornado Restricted Stock or Operating Partnership Units Narrative) (Details) - USD ($) $ in Thousands	9 Months Ended	12 Months Ended
Sep. 30, 2019	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Restricted Operating Partnership Units Plan
Share Based Compensation Equity Instruments Other Than Stock Options And Restricted Stock Units Summary
Award vesting period (years)		4 years
Distributions, share-based compensation		$ 4,070	$ 2,559	$ 2,310
Grant-date fair value		58,732	17,463	24,927
Vested in period, fair value		27,821	18,037	20,903
Restricted Stock Units RSU
Share Based Compensation Equity Instruments Other Than Stock Options And Restricted Stock Units Summary
Award vesting period (years)	4 years
Distributions, share-based compensation		51	44	46
Grant-date fair value		568	623	601
Vested in period, fair value		$ 477	$ 492	$ 645

Amount of paid and unpaid cash, stock, and paid-in-kind dividends declared for award under share-based payment arrangement.

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- Definition

Period over which grantee's right to exercise award under share-based payment arrangement is no longer contingent on satisfaction of service or performance condition, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days. Includes, but is not limited to, combination of market, performance or service condition.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (a)(1)
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- Definition

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.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (d)(2)
-URI http://asc.fasb.org/extlink&oid=116856206&loc=d3e5070-113901

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- Definition

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).

+ References

No definition available.

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- References

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