Stock-based Compensation (Narrative) (Details)		3 Months Ended		6 Months Ended
	Mar. 30, 2020 USD ($) component	Jun. 30, 2020 USD ($)	Jun. 30, 2019 USD ($)	Jun. 30, 2020 USD ($)	Jun. 30, 2019 USD ($)
Out Performance Plan 2020
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Out of performance plan notional amount	$ 35,000,000
Grant-Date Fair Value	11,686,000
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		$ 4,103,000
Award vesting period	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%
Executive Officer | Out Performance Plan 2020
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Out of performance plan notional amount granted	$ 32,930,000
Absolute | Out Performance Plan 2020
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Duration of performance measurement period	3 years
Required shareholder return three year	21.00%
Absolute | Maximum | Out Performance Plan 2020
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage awards will be reduced if total shareholder return Is zero or negative	50.00%
Relative | Out Performance Plan 2020
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Required shareholder return under relative component	2.00%
Percentage of shareholder return under which no awards will be earned	0.00%
Relative | Maximum | Out Performance Plan 2020
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage awards will be reduced if total shareholder return Is zero or negative	50.00%
Relative | SNL US Office REIT Index | Out Performance Plan 2020
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Required shareholder return per year	80.00%
Relative | SNL US Retail Index | Out Performance Plan 2020
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Required shareholder return per year	20.00%
General and Administrative Expense
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation expense		$ 7,703,000	$ 10,520,000	$ 33,468,000	$ 42,174,000