Deferred Costs, Acquired Lease Intangibles and Goodwill - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016	Dec. 31, 2016
Deferred Costs [Line Items]
Amortization expense related to deferred leasing costs	$ 5,900	$ 5,700	$ 12,100	$ 11,500
Revenue related to amortization of acquired above- and below-market leases, net	1,100	900	2,548	5,075
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	4,600	$ 7,000	9,000	$ 14,700
Unsecured revolving credit facility | Unsecured term loan facility
Deferred Costs [Line Items]
Net deferred financing costs	$ 3,400		$ 3,400		$ 4,500