Stock-based Compensation (Performance Conditioned AO LTIP Units Vornado Stock Options) (Details) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2019 USD ($) $ / shares shares
Vornado stock options
Shares
Options outstanding at beginning of period (shares) | shares	2,280,126
Granted (shares) | shares	35,106
Exercised (shares) | shares	(534,972)
Cancelled or expired (shares) | shares	(11,383)
Options outstanding at end of period (shares) | shares	1,768,877
Options vested and expected to vest at end of period (shares) | shares	1,767,546
Option exercisable at end of period (shares) | shares	1,693,192
Weighted- Average Exercise Price
Options outstanding at beginning of period (in usd per share) | $ / shares	$ 50.81
Granted (in usd per share) | $ / shares	62.68
Exercised (in usd per share) | $ / shares	29.25
Cancelled or expired (in usd per share) | $ / shares	78.07
Options outstanding at end of period (in usd per share) | $ / shares	57.39
Options vested and expected to vest at end of period (in usd per share) | $ / shares	57.37
Options exercisable at end of period (in usd per share) | $ / shares	$ 56.87
Weighted- Average Remaining Contractual Term
Options outstanding, Weighted Average Remaining Contractual Term	1 year 1 month 6 days
Options vested and expected to vest, Weighted Average Remaining Contractual Term	1 year 1 month 6 days
Options exercisable, Weighted Average Remaining Contractual Term	9 months 18 days
Aggregate Intrinsic Value
Options outstanding, Aggregate Intrinsic Value | $	$ 16,247
Options vested and expected to vest, Aggregate Intrinsic Value | $	16,246
Options exercisable, Aggregate Intrinsic Value | $	$ 16,133
Performance Conditioned AO LTIP Units
Shares
Granted (shares) | shares	496,762
Options outstanding at end of period (shares) | shares	496,762
Weighted- Average Exercise Price
Granted (in usd per share) | $ / shares	$ 62.62
Options outstanding at end of period (in usd per share) | $ / shares	$ 62.62
AO LTIP Units
Shares
Options outstanding at beginning of period (shares) | shares	183,233
Granted (shares) | shares	207,808
Vested (shares) | shares	(46,285)
Cancelled or expired (shares) | shares	(7,058)
Options outstanding at end of period (shares) | shares	337,698
Weighted- Average Exercise Price
Options outstanding at beginning of period (in usd per share) | $ / shares	$ 70.34
Granted (in usd per share) | $ / shares	62.66
Vested (in usd per share) | $ / shares	70.31
Cancelled or expired (in usd per share) | $ / shares	67.59
Options outstanding at end of period (in usd per share) | $ / shares	$ 65.67