Stock-based Compensation (Out Performance Plans Narrative) (Details)			12 Months Ended
	Mar. 30, 2020 USD ($) component	Mar. 15, 2018	Dec. 31, 2020 USD ($) shares	Dec. 31, 2018 USD ($) component
Full Value Awards
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares authorized (in shares) | shares			4,662,000
OPPs
Out Performance Plan
Share-based compensation expense			$ 7,583,000	$ 8,040,000
Out Performance Plan 2020
Out Performance Plan
Out of performance plan notional amount	$ 35,000,000		35,000,000
Grant-date fair value	11,686,000		$ 11,700,000
Amount expensed immediately	$ 7,583,000
Revised age limit fo awards vesting criteria	65 years
Revised age for vesting with years of service	60 years
Years of service	20 years
Out performance plan notional amount remaining	$ 4,103,000
Award vesting period (years)	5 years
Number of components of out performance plan | component	2
Amount of basis points by which Vornado underperforms the index	2.00%
Amount of basis points by which Vornado underperforms the index, total	6.00%
Percentage of notional amount granted			94.00%
OPP Units Earned			To be determined in 2023
Out Performance Plan 2020 | Executive Officer
Out Performance Plan
Notional amount granted	$ 32,930,000
Out Performance Plan 2018
Out Performance Plan
Out of performance plan notional amount			$ 35,000,000	$ 35,000,000
Grant-date fair value			$ 10,300,000
Number of components of out performance plan | component				2
Amount of basis points by which Vornado underperforms the index				2.00%
Amount of basis points by which Vornado underperforms the index, total				6.00%
Percentage of notional amount granted			78.20%
OPP Units Earned			To be determined in 2021
Out Performance Plan 2017
Out Performance Plan
Out of performance plan notional amount			$ 35,000,000
Grant-date fair value			$ 10,800,000
Percentage of notional amount granted			86.60%
Absolute | Out Performance Plan 2020
Out Performance Plan
Duration of performance measurement period	3 years
Required shareholder return three year	21.00%
Absolute | Out Performance Plan 2020 | Maximum
Out Performance Plan
Percentage awards will be reduced if total shareholder return is zero or negative	50.00%
Absolute | Out Performance Plan 2018
Out Performance Plan
Duration of performance measurement period		3 years		3 years
Required shareholder return three year				21.00%
Relative | Out Performance Plan 2020
Out Performance Plan
Required shareholder return under relative component	2.00%
Percentage of shareholder return under which 50% of awards will be earned	0.00%
Relative | Out Performance Plan 2020 | Maximum
Out Performance Plan
Percentage awards will be reduced if total shareholder return is zero or negative	50.00%
Relative | Out Performance Plan 2018
Out Performance Plan
Percentage awards will be reduced if total shareholder return is zero or negative				0.00%
Required shareholder return under relative component				3.00%
Relative | Out Performance Plan 2018 | Maximum
Out Performance Plan
Percentage awards will be reduced if total shareholder return is zero or negative				50.00%
SNL US Office REIT Index | Relative | Out Performance Plan 2020
Out Performance Plan
Required shareholder return per year	80.00%
SNL US Office REIT Index | Relative | Out Performance Plan 2018
Out Performance Plan
Required shareholder return per year				70.00%
SNL US Retail Index | Relative | Out Performance Plan 2020
Out Performance Plan
Required shareholder return per year	20.00%
SNL US Retail Index | Relative | Out Performance Plan 2018
Out Performance Plan
Required shareholder return per year				30.00%
2019 Omnibus Share Plan | Full Value Awards | Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares authorized (in shares) | shares			5,500,000
2019 Omnibus Share Plan | Not Full Value Awards | Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares authorized (in shares) | shares			11,000,000