Commitments and Contingencies (Details) - USD ($)	3 Months Ended
	Mar. 31, 2018	Sep. 30, 2016
Other Commitments
Guarantees and master leases	$ 647,000,000
Outstanding letters of credit	8,921,000
Commitment to fund additional capital to partially owned entities	52,000,000
Construction commitment	389,000,000
General Liability
Insurance
Insurance limit per property	300,000,000
Insurance limit per occurrence	300,000,000
All Risk And Rental Value
Insurance
Insurance limit per occurrence	2,000,000,000.0
Earthquake California Properties
Insurance
Insurance limit per occurrence	180,000,000
Insurance maximum coverage limit in aggregate	$ 180,000,000
Vornado deductible, percentage of property value	5.00%
Terrorism Acts
Insurance
Insurance limit per occurrence	$ 4,000,000,000
Insurance maximum coverage limit in aggregate	4,000,000,000
NBCR Acts
Insurance
Insurance limit per occurrence	2,000,000,000
Insurance maximum coverage limit in aggregate	$ 2,000,000,000
Insurance coverage end date	December 2020
PPIC | NBCR Acts
Insurance
Insurance deductible	$ 1,601,000
Insurance deductible percentage of balance of covered loss	18.00%
Moynihan Office Building
Other Commitments
Equity method ownership percentage		50.10%