Deferred Costs, Acquired Lease Intangibles and Goodwill - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016
Deferred Costs [Line Items]
Amortization expense related to deferred leasing costs	$ 5,800	$ 6,100	$ 17,900	$ 17,600
Revenue related to amortization of acquired above- and below-market leases, net	1,600	1,200	4,154	6,285
Goodwill	491,479		491,479		$ 491,479
Observatory
Deferred Costs [Line Items]
Goodwill	227,500		227,500
Real estate
Deferred Costs [Line Items]
Goodwill	264,000		264,000
Lease agreements
Deferred Costs [Line Items]
Amortization expense related to acquired lease intangibles	4,000	$ 5,000	13,000	$ 19,700
Unsecured revolving credit facility | Unsecured term loan facility
Deferred Costs [Line Items]
Net deferred financing costs	$ 8,700		$ 8,700		$ 4,500