Deferred Costs, Acquired Lease Intangibles and Goodwill - Narrative (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2013
Deferred Costs [Line Items]
Amortization of deferred leasing and acquired deferred leasing costs	$ 24,500	$ 26,300	$ 24,100
Amortization of acquired above and below-market leases, net	7,311	6,120	5,721
Goodwill	491,479	491,479
Empire State Building observatory operations
Deferred Costs [Line Items]
Goodwill				$ 227,500
Empire State Building
Deferred Costs [Line Items]
Goodwill				250,800
501 Seventh Avenue
Deferred Costs [Line Items]
Goodwill				$ 13,200
Lease agreements
Deferred Costs [Line Items]
Amortization expense related to acquired lease intangibles	$ 10,900	12,100	$ 17,100
Ground lease
Deferred Costs [Line Items]
Weighted-average amortization period	24 years 1 month 6 days
In-place leases and deferred leasing costs
Deferred Costs [Line Items]
Weighted-average amortization period	3 years 10 months 24 days
Above-market leases
Deferred Costs [Line Items]
Weighted-average amortization period	2 years 10 months 24 days
Below-market Lease
Deferred Costs [Line Items]
Weighted-average amortization period	3 years 10 months 24 days
Unsecured revolving credit facility | Revolving Credit Facility
Deferred Costs [Line Items]
Net deferred financing costs	$ 4,200	$ 6,300