Stock-based Compensation (Vornado Stock Options) (Details) - USD ($)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Share Based Compensation Employee Stock Purchase Plan Activity
Share Based Compensation Expense	$ 33,980,000	$ 39,846,000	$ 36,641,000
Employee Stock Option
Share Based Compensation Employee Stock Purchase Plan Activity
Share Based Compensation Expense	937,000	$ 1,298,000	$ 4,550,000
Compensation Cost Not Yet Recognized	$ 1,335,000
Compensation Cost Recognition Period	1 year 8 months
Award Vesting Period	4 years
Grant Date Fair Value Of Options (in dollars per shares)	$ 22.14	$ 28.85	$ 20.31
Stock options expiration term	10 years
Cash Received From Exercise Of Stock Options	$ 6,825,000	$ 15,343,000	$ 17,441,000
Total Intrinsic Value Of Options Excercised	$ 5,519,000	$ 3,873,000	$ 18,223,000
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Number, Beginning Balance	2,827,570
Stock Options Granted Shares	42,466
Stock Options Exercised Shares	(125,724)
Stock Options Cancelled or Expired Shares	(11,768)
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Number, Ending Balance	2,732,544	2,827,570
Options Vested And Expected To Vest Shares	2,737,594
Options Excercisable Shares	2,642,684
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price, Beginning of Period	$ 60.06
Stock Options Granted Weighted Average Exercise Price	92.97
Stock Options Exercised Weighted Average Exercise Price	56.44
Stock Options Cancelled or Expired Weighted Average Exercise Price	100.49
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price, End of Period	65.76	$ 60.06
Options Vested And Expected To Vest Weighted Average Exercise Price	60.66
Options Excercisable Weighted Average Exercise Price	$ 59.42
Options Outstanding Weighted Average Remaining Contractual Term	3 years 1 month
Options Vested And Expected To Vest Weighted Average Remaining Contractual Term	4 years 1 month
Options Exercisable Weighted Average Remaining Contractual Term	2 years 11 months
Options Outstanding Aggregate Intrinsic Value (in US dollars)	$ 120,360,377
Options Vested And Expected To Vest Aggregate Intrinsic Value (in US dollars)	118,170,212
Options Excercisable Aggregate Intrinsic Value (in US dollars)	$ 119,269,973
Expected Volatility Rate	35.00%	35.00%	36.00%
Expected Life	5 years	5 years	5 years
Risk Free Interest Rate	1.76%	1.56%	1.81%
Risk Expected Dividend Yield (in percentage)	3.20%	3.30%	4.10%