Stock-based Compensation (Narrative) (Details)			3 Months Ended		6 Months Ended
	Mar. 15, 2018 USD ($) component	Jan. 12, 2018 USD ($)	Jun. 30, 2018 USD ($)	Jun. 30, 2017 USD ($)	Jun. 30, 2018 USD ($)	Jun. 30, 2017 USD ($)
Share Based Compensation Arrangement By Share Based Payment Award
Share-based compensation expense			$ 6,976,000	$ 6,724,000	$ 20,645,000	$ 20,283,000
AO LTIP Units
Share Based Compensation Arrangement By Share Based Payment Award
Threshold level					100.00%
Amortization Period		4 years			4 years
Period from grant date		10 years
Grant-Date Fair Value		$ 3,484,000	2,862,000		$ 2,862,000
Amount expensed immediately		$ 622,000
Revised age limit for awards vesting criteria					65 years
Revised age limit for vesting with years of service					60 years
Years of service					20 years
Special allocation (percent)					10.00%
Special distribution (percent)					10.00%
Out Performance Plan 2018
Share Based Compensation Arrangement By Share Based Payment Award
Amortization Period					5 years
Grant-Date Fair Value	$ 10,283,000		$ 2,243,000		$ 2,243,000
Amount expensed immediately	$ 8,040,000
Revised age limit for awards vesting criteria	65 years
Revised age limit for vesting with years of service	60 years
Years of service	20 years
Out performance plan notional amount	$ 35,000,000
Amount by which vornado underperforms the index (basis points)	2.00%
Amount by which vornado underperforms the index, total (basis points)	6.00%
Number of components of out performance plan | component	2
Relative | Out Performance Plan 2018
Share Based Compensation Arrangement By Share Based Payment Award
Required shareholder return under relative component	3.00%
Percentage of shareholder return under which no awards will be earned	0.00%
Absolute | Out Performance Plan 2018
Share Based Compensation Arrangement By Share Based Payment Award
Duration of performance measurement period	3 years
Required shareholder return three year	21.00%
SNL US Office REIT Index | Relative | Out Performance Plan 2018
Share Based Compensation Arrangement By Share Based Payment Award
Required shareholder return per year	70.00%
SNL US Retail Index | Relative | Out Performance Plan 2018
Share Based Compensation Arrangement By Share Based Payment Award
Required shareholder return per year	30.00%
Maximum | Relative | Out Performance Plan 2018
Share Based Compensation Arrangement By Share Based Payment Award
Percentage awards will be reduced if TSR is zero or negative or Negative	50.00%
Senior Executive | Out Performance Plan 2018
Share Based Compensation Arrangement By Share Based Payment Award
Out performance plan amount granted	$ 27,354,000