COVID-19 Pandemic - Narrative (Details) - COVID-19	3 Months Ended	6 Months Ended
	Jun. 30, 2020 USD ($)	Jun. 30, 2020 USD ($)	Jul. 31, 2020 employee	Apr. 30, 2020 employee	Apr. 01, 2020 USD ($)
Unusual or Infrequent Item, or Both [Line Items]
Number of employees furloughed				1,803
Rent collected, percent	88.00%
Rent collected (including deferrals), percent	94.00%
Write off of tenant receivables deemed uncollectible | $	$ 8,822,000	$ 8,822,000
Office Space
Unusual or Infrequent Item, or Both [Line Items]
Rent collected, percent	93.00%
Rent collected (including deferrals), percent	98.00%
Retail
Unusual or Infrequent Item, or Both [Line Items]
Rent collected, percent	72.00%
Rent collected (including deferrals), percent	78.00%
330 West 34th Street
Unusual or Infrequent Item, or Both [Line Items]
Write off of receivables arising from the straight-lining of rents | $	$ 36,297,000	$ 36,297,000
Non-Management Member Board of Trustees
Unusual or Infrequent Item, or Both [Line Items]
Annual cash retainer forgone | $					$ 75,000
Subsequent Event [Member]
Unusual or Infrequent Item, or Both [Line Items]
Number of employees returned from furlough			542
Building Maintenance Service LLC
Unusual or Infrequent Item, or Both [Line Items]
Number of employees furloughed				1,293
Building Maintenance Service LLC | Subsequent Event [Member]
Unusual or Infrequent Item, or Both [Line Items]
Number of employees returned from furlough			503
Hotel Pennsylvania
Unusual or Infrequent Item, or Both [Line Items]
Number of employees furloughed				414
Vornado Realty Trust
Unusual or Infrequent Item, or Both [Line Items]
Number of employees furloughed				96
Vornado Realty Trust | Subsequent Event [Member]
Unusual or Infrequent Item, or Both [Line Items]
Number of employees returned from furlough			39