Basis of Presentation and Significant Accounting Policies (Estimated Taxable Income) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Reconciliation of Net income to Estimated income tax payable
Net income attributable to common shareholders	$ 651,181	$ 66,125	$ 220,463	$ (114,163)	$ 230,742	$ 198,870	$ 165,651	$ 84,593	$ 823,606	$ 679,856	$ 783,388
Net gain on extinguishment of Skyline properties debt									(457,970)	0	0
Depreciation and Amortization									302,092	227,297	219,403
Impairment losses on marketable equity securities									170,332	20,281	34,670
Earnings of partially owned entities									(149,094)	(5,299)	71,960
Straight-line rent adjustments									(137,941)	(144,727)	(77,526)
Sale of real estate and other capital transactions									(39,109)	320,326	(477,061)
Vornado Stock Options									(3,593)	(8,278)	(9,566)
Tangible Property Regulations									0	(575,618)	0
Other, net									9,121	(26,114)	(33,410)
Estimated Taxable Income (unaudited)									517,444	$ 487,724	$ 511,858
Net Basis Difference Of Assets And Liabilities Between Tax Basis And GAAP Basis	$ 3,700,000								$ 3,700,000