Deferred Costs, Acquired Lease Intangibles and Goodwill - Narrative (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2013
Deferred Costs [Line Items]
Amortization of deferred leasing and acquired deferred leasing costs	$ 24,100	$ 24,200	$ 25,400
Amortization of acquired above and below-market leases, net	5,721	8,795	19,353
Goodwill	491,479	491,479
Empire State Building observatory operations [Member]
Deferred Costs [Line Items]
Goodwill				$ 227,500
Empire State Building [Member]
Deferred Costs [Line Items]
Goodwill				250,800
501 Seventh Avenue [Member]
Deferred Costs [Line Items]
Goodwill				$ 13,200
Lease agreements [Member]
Deferred Costs [Line Items]
Amortization expense related to acquired lease intangibles	$ 17,100	24,600	$ 37,700
Ground lease [Member]
Deferred Costs [Line Items]
Weighted-average amortization period	25 years
In-place leases and deferred leasing costs [Member]
Deferred Costs [Line Items]
Weighted-average amortization period	4 years 10 months
Above-market leases [Member]
Deferred Costs [Line Items]
Weighted-average amortization period	3 years 10 months 24 days
Below-market Lease [Member]
Deferred Costs [Line Items]
Weighted-average amortization period	4 years 2 months
Unsecured revolving credit facility [Member] | Revolving Credit Facility [Member]
Deferred Costs [Line Items]
Net deferred financing costs	$ 8,300	$ 4,500